Mary was last seen at her home in West Willow, Pennsylvania on June 5, 1984. Her estranged husband, Jere, went to pick her up to look at a car she was thinking of buying, but Mary wasn't ready to go. Her husband took their son to nearby Long's Park and when they returned, she was gone. She left a note saying she was going to walk to a local Turkey Hill store, but clerks at the store don't remember seeing her there. She has never been heard from again.

Mary and Jere were in the process of a divorce in 1984 and Jere was living with his parents, but they remained in regular contact. She disappeared the day before a custody hearing over their child. Foul play is suspected in her case, as it's uncharacteristic of her to leave without warning.