Demyon was last seen driving away from his townhouse on Gurteen Court in Cockeysville, Maryland at approximately 6:15 p.m. on January 13, 1997. He said he was going to use a pay phone at a nearby motel, as his home telephone had been disconnected. He never returned home and has never been heard from again. He was reported missing by his wife on the day after his disappearance.

Demyon's dark blue 1989 Pontiac Bonneville was found on February 20, 1997, in the 1800 block of north Calvert Street in Baltimore City, Maryland. No evidence of foul play and no clues to Demyon's whereabouts were discovered at the scene.

Authorities believe Demyon may have been murdered. He was the vice president of Safety/Sight Incorporated in 1997; the company had been founded by his father. Demyon was an avid gambler, particularly at horse races, in 1997 and frequented Las Vegas, Nevada and Atlantic City, New Jersey. He was apparently in debt to several gambling associates, but his wife stated none of his debts were big enough to make someone want to harm him. His case remains unsolved.