Mark David Thomas was 30 when he was last heard from in Oklahoma City on January 5, 1986. He is described as a Caucasian male, brown hair and brown eyes, 5 feet 9 inches tall and weighing about 145–150 pounds. What he was wearing and the circumstances of his disappearance are not known publicly.

His disappearance is listed in NamUs as MP77009 and the Oklahoma Department of Corrections handled the investigation. Little is available about his personal life, including occupation, family or habits, which has made reconstructing his movements before January 5 difficult. The case remains open and is noted among long-unsolved disappearances in Oklahoma.

Did anyone in Oklahoma City in early 1986 have contact with Mark or recall seeing him around January 5?