The research was exotic and, to anthropologist Rachel Hunt, irreplaceable. Hunt had just finished spending 3 1/2 months on a tiny island off Puerto Rico studying mother-infant relationships among rhesus monkeys for her master's thesis.

But within 45 minutes of landing at National Airport Wednesday night, it was all gone. All of Hunt's notes, film, camera and other items documenting her work were stolen by a thief who broke into the back of her fiance's locked car while the couple was having dinner, she told D.C. police.

"I'm kind of in shock," said Hunt, 28, a graduate student at the State University of New York at Buffalo and resident of Alexandria. "This is my master's thesis that just went down the drain . . . . That was every piece of data I've collected over the past 3 1/2 months."

Her research on the island of Cayo Santiago focused on the varied behaviors 9- to-11-month-old monkeys demonstrate when their mothers mate once again, and the photographs were taken to back up her observations.

"You learn how to identify individuals, and I feel like I just lost pictures of 48 close friends," she said.

Of the data she said, "You can't get it again, because it's of a specific birth-group of animals and they'll never be the same ages again." She said she gave up a teaching assistantship and borrowed $5,000 to do the field work. "I was just so lucky to be able to go," she said. "I've seen everything I was able to see, but the data I can't replace at all."

The golden brown, 20- to 40-pound rhesus macaques monkeys are descendants of primates introduced in 1938 to Cayo Santiago, a research island maintained by the Caribbean Primate Research Center, which is affiliated with the National Institutes of Health and the University of Puerto Rico Medical School.

A black duffle bag containing Hunt's work disappeared while Hunt and Stephen Qualiana of Gaithersburg were having a quick dinner in the 700 block of Seventh Street NW. Three other bags in the back were not touched.

Police -- who step up warnings during holiday season about leaving packages and other tempting items exposed in parked cars -- said they did not know how the thief got into Qualiana's 1974 Datsun.

"It's one of the seasonal problems," said D.C. police spokesman Joseph Gentile. "People should put whatever gifts they get or buy into the trunk of their cars so they can't be seen . . . Out of sight, out of mind."

Hunt and Qualiana, chief copy editor for the Gazette newspapers in Gaithersburg, "looked in alleys, dumpsters, all over the area," Hunt said. "We put up signs offering a $100 reward," and took fliers to businesses in the area, she said.