One by one, D.C. police officers and recruits had peered inside a locked Nissan Altima parked 40 feet from where 7-year-old Michael Kingsbury walked out of his apartment and disappeared into the Trinidad neighborhood last summer wearing a red shirt and a pull-up diaper.

One officer said he did a “close, visual sweep” of cars parked in the alley and was “extremely certain” that Michael, who had autism, was not inside. Another reported that “the front seat and back seat were cleared off.” Others also said they saw nothing in the car; some pulled door handles, but none forced their way inside.

Michael’s 4-foot-3-inch, 60-pound body was found the evening of July 8 — about 32 hours after his mother’s first call to 911 — facedown on the floorboard in the back of the broken-down Altima. It was a veteran detective who finally found Michael after spotting a soiled diaper decorated with a “Monsters Inc.” design on the back seat, although officials don’t know whether the diaper was there for the entire search, or whether the boy had taken it off even as dozens of officers scanned the neighborhood looking for him.

The medical examiner said it appeared Michael succumbed to the sweltering heat. “We did the best we could,” an academy recruit later told an investigator.

D.C. police say an internal review sparked by Michael’s tragic death has highlighted particular challenges in searches for autistic children who become lost and for elderly people with dementia or Alzheimer’s. It has led to policy changes that they hope will improve their response to a growing problem.

The Centers for Disease Control and Prevention says that one in 68 children in the United States have autism, up from one in 88 two years ago. Many have a tendency to wander.

“Michael’s story was like so many others that have touched all of our hearts, and energized us to do more to save these children,” said Robert G. Lowery Jr., an official at the National Center for Missing & Exploited Children, based in Alexandria. “These children are finding themselves in high-risk situations.”

In the 198-page report on the search for Michael, obtained by The Washington Post under the Freedom of Information Act, police say they must do a better job of quickly learning the mannerisms, habits and limitations of autistic children who go missing, searching for hints that might lead them to hiding places. A teacher told a detective that Michael was “always hungry,” liked to climb shelves, ran from his classroom, often opened and closed doors, and would remove his diaper when it was wet.

But that interview did not take place until five days after Michael’s body was found, according to the date on the detective’s notebook. Dispatchers talking to police officers at the start of the search had gathered basic details — Michael’s description, that he had autism, that he had wandered from home before, and that he “does not speak well, but will respond to his name.”

Capt. Lewis J. Douglas Jr., a supervisor in the Youth Investigations Division, which handles missing-persons cases, said in the report that “the first officer on the scene should determine what interests the missing person has, are they fascinated with anything, to include items, areas or persons.” He said Michael’s case should have been called a “search and rescue mission,” adding more urgency and perhaps a different search pattern, because the boy “did not have the capability to comprehend complex reasoning.”

Douglas emphasized that “the last known location where a missing person was last seen must be thoroughly searched. Even if someone said it was searched, it should be searched again.” He said that includes “under crawl spaces and inside of vehicles to include the floorboards. . . .  Anywhere you can see is anywhere a person with autism can become disoriented.”

Lowery, of the center for missing and exploited children, said children with autism tend to gravitate toward water and confined spaces, “making them hard to find.”

His group helped police in New York during the highly publicized search for 14-year-old Avonte Oquendo, who had autism. He walked out of his Queens school in October and was found dead near the East River in January. There have been several other similar cases recently, some ending well.

D.C. Police Cmdr. Daniel P. Hickson, who heads the Youth Investigations Division, said the report has led to more detailed and better-documented searches in which many people retrace old ground to ensure “new eyes” are present. Dogs are sometimes sent in first, so they can more easily follow scents on untrampled ground, followed by human searchers assigned to grids.

“Under ideal circumstances, you want to know as much as you can as quick as you can,” Hickson said. “Does the person have a fascination with trains, for example? If so, then we need to quickly mark out a path from where he went missing to the nearest Metro.”

Hickson said it’s impossible to know whether learning more details about Michael may have led police to the boy more quickly. He said searchers did know the boy wore a diaper. But he also said there could have been better coordination among the searchers.

How Michael was missed may never be known.

“I’m not sure we’ll ever be able to answer that with certainty,” Hickson said. “What we can do in the future is try and ensure that we do everything very thoroughly and very accurately. . . . The goal is that we want to find and return every missing person.”

Hundreds of reports of missing persons are investigated in the District every year, and the vast majority of them are quickly found.

And although the changes outlined in the report stem from an effort to improve searches for vulnerable residents who become lost, they also may translate to other missing-persons cases. Some of the new techniques were used in the recent search of a park for missing 8-year-old Relisha Rudd, who police say was abducted.

After Michael’s body was discovered, a television news camera captured a detective’s angry shout and his furious pounding of his fists into the hood of a police car. Michael’s family, neighbors, lawmakers and police grappled with a single question: Why was the little boy not found sooner?

The people who lived along Northeast Washington’s West Virginia Avenue in Trinidad blamed themselves as much as they did authorities, questioning their own commitment to a neighborhood struggling with poverty and crime. The search for Michael was comprehensive, involving a helicopter, dogs and dozens of officers and volunteers who scoured the streets, alleys and boarded-up houses. They followed several trails sniffed out by search dogs and investigated bloodstains in a vacant house on Michael’s block.

Repeatedly, searchers were drawn to the beige 2002 Altima parked next to a collection of trash cans and buckets. Its windows were clear of tint, the doors locked and the battery dead. The owner said she wasn’t sure whether she had locked its doors.

The first officer to take the missing-person call on July 7 checked the Nissan, reporting only that it was locked. A half-hour later, two other officers checked the vehicle. Between 1:30 p.m. and 2 p.m., a different officer “looked through the driver’s side window of the Altima and observed nobody inside,” a police report says. On July 8, just after midnight, still another officer reported the car empty.

Between 9 a.m. and 9:30 a.m., a recruit said he looked inside, noticed the light-colored interior, but nothing on the seats. A second recruit inspected the car about 10 a.m. “I knocked on the trunk and called Michael’s name,” the cadet said in a report. “I checked all four doors, they were locked. I looked through the windows, I didn’t see anything. I pulled the door handle again and I called his name again. I looked in the back seat and didn’t see anything. I wanted to make sure no one was asleep in the car.”

About 5:40 p.m., Detective Jonathan Andrews Sr., a 24-year veteran, was in a meeting in the command bus near the boy’s home. Through a window, he saw a Chevrolet Impala and the Altima, and recalled a New Jersey case in which three children playing hide-and-seek got trapped in the trunk of an abandoned car.

“I advised that I was going to check those vehicles and attempt to ‘pop’ the trunk,” Andrews wrote in his report. His supervisor replied, “Go for it.”

He walked around the Impala, then circled the Altima. “I noticed a diaper or babies pull-up sitting in the back inside the vehicle,” Andrews wrote. He looked again, he said, and saw Michael curled up on the floorboard. There were small handprints on the inside glass window.