Came across this story of Ronald Tammen. A member of Delta Tau Delta, he disappeared from Miami's Fisher Hall in 1953. Here is a synopsis from Wikipedia and a link from the Miami University's Alumni Association about the mystery.
"Tammen, a student at Miami University, left his Fisher Hall room at approximately 8 p.m. on 19 April 1953 to get new bed sheets from the Hall manager because a prankster had put a fish in his bed. Tammen took the sheets and returned to his dorm room to study psychology, which was the last time he was definitely seen. At 10:30, Tammen's roommate returned to find Tammen's psychology book lying open on his desk and all the room lights on, but Tammen was not there. When Tammen failed to return the following day, a search began. To this day, Tammen's fate remains unknown."
https://www.miamialum.org/s/916/22/I...id=1&cid=26687