Shea departed from her family's residence in the 500 block of 14th Street in Tyrone, Pennsylvania at 12:00 p.m. on March 18, 1965. That day she attended her morning classes, then went home for lunch. Her father offered to drive her back to school for her afternoon classes, but she said she would rather walk. Shea was last seen walking northbound between 15th Street and 16th Street at the time of her disappearance. A crossing guard helped her across 15th Street, then she stopped to chat with a neighbor, who was the last person to see her before she vanished. The neighbor stated that Shea was in good spirits at the time. She continued onward after finishing the conversation, but never arrived at the school, which was four blocks from her home.

Shea's disappearance was not noticed until 4:45 p.m., when she failed to return home from school. A search was launched, but there was no sign of her. Bloodhounds traced Shea's scent to Garfield Street, just one block from her school, then lost the trail. She has never been heard from again and little evidence is available as to her fate.

Shea lived with her parents and two younger brothers in 1965, and her parents had another daughter after she vanished. Her mother died in 1997 and her father in 2006. One of her brothers has remained in Pennsylvania, the other now lives in Ohio, and her younger sister lives in Florida. Her case remains unsolved.