On the afternoon of Thursday, April 3, Rick Shelton left work at the Smithsonian Institution early and stopped by the Maine Avenue waterfront to pick up a bushel of oysters. His only sister was getting married that weekend in Columbus, Ohio and he was going to swing by Cincinnati to pick up his girlfriend for the big event.

The bearded, 29-year-old industrial designer left by car at 7 p.m. He hasn't been heard from since.

His gold 1968 Cougar was spotted on April 3 or 4 on the gravel shoulder of a two-lane highway in the Blue Ridge Mountains of Southwest Virginia, about eight miles from Hillsville, population 1,200.

The keys were in the ignition, the gasoline tank was empty. The oysters sat rotting on the back seat next to Shelton's duffel bag. Empty beer and liquor bottles littered the floor -- which is strange, friends say, since Shelton does not drink.

Forensic experts from Hillsville's sheriff's department say there were no signs of a struggle. There were no signs of Shelton either.

"Here's what puzzles me," said Hillsville Sheriff W. Hassell Vass. "Why would the man have been coming down here when he was going up to Ohio? . . . We've got all kinds of samples, fingerprints, hair samples and everything, but I just can't figure it out."

Another thing Vass said he cannot figure out is how the car got to Hillsville. "We have witnesses who spotted the car on the morning of April 3," Vass said, hours before friends in Washington said Shelton left.

"Like I told the boys," the sheriff said, "I don't believe the man ever left Washington."

But friends think Shelton did leave Washington. After checking out of work -- where he had been designing a set for an Arts and Industry Building exhibit on Louisiana Music -- at 3:30 p.m., he bought the oysters and then returned home to the Eastern Power Boat Club on the Potomac off Water and 13th streets SE. He had been living there since March aboard an old 42-foot cruiser he had recently bought for renovation.

Clifton Fleshman, the custodian at the boat yard, was the last person known to have seen Shelton in Washington. "He came home and then two friends came over to help him work on the boat a little and then pack," Fleshman said. "After the friends left he asked me to make an adjustment to his carburetor, I did and he left. He told me he'd see me on Monday."

Somewhere along the line, however, something went wrong. District police say they have no clues. Sheriff Vass' mountain-trained force is baffled. A private detective out of Columbus was on his way to Hillsville last night, and $1,000 in reward money is being offered by Shelton's friends.

"There aren't any leads," said the private detective, who asked to remain anonymous. "We do know he was in the habit of picking up hitchhikers, and that he didn't have any credit cards or checking accounts so he was probably carrying a few hundred dollars in cash with him."

Officer Charlie Gallup of the D.C. Police Department's missing persons bureau said Shelton's case "is out of the ordinary. It could go either way. He could be all right and just not want to be bothered. He could be sick or injured somewhere. Or there could have been foul play involved."

As the days of Shelton's absence roll by Shelton's friends and relatives say they have given up hoping for his safe return.

He is described by friends and family, in past tense, as a fre-spirited outdoorsman who enjoyed scuba diving and as a kind family-oriented young man who held degrees in both education and industrial design.

"The guy had so much to live for. He wasn't like a bum or anything, he would have called us and told us if he couldn't make the wedding," said longtime friend Hugo Cabrerra.

"He was very serious about his work -- when he was in school he would buy something like razor blades and try and envision better ways of packaging it. He was a great artist and a great, caring friend."

"We're real low right now," said Shelton's father, Irving.

"I don't think there's any possibility he's alive," he said. 'I just hope they find his body right quick."