Fascinating rabbit hole!
1953: College sophomore (good student, musician, athlete) is last seen getting a set of clean sheets to change the ones on his bed which had fallen victim to a college prank. His room is found with the light on, textbook open on desk, and bed almost made up with clean sheets (pillow case remaining). Theories include speculations about FBI, hypnosis, amnesia, his psych professor, and much more. A lot of thorough research carefully compiled at this site: ronaldtammen.com