Reidenbach attended her classes at Seneca Valley High School on October 6, 1981, had her senior class picture taken, and went to Zelienople, Pennyslvania afterwards. She had an after-school job at an appliance store, Mel Den, in the 200 block of south Main Street. She usually worked there with a classmate, but her co-worker was sick and did not report to work.

At 4:30 p.m., Reidenbach left the store and walked approximately one block to a pharmacy to buy cold medicine, as she was feeling ill. It was established that Reidenbach did arrive in the store and purchased the medicine. She was last seen in a supermarket parking lot on south Main Street. She never went back to her job and has never been heard from again. She left her purse, schoolbooks, and cigarettes behind at Mel Den when she vanished. She also left $100 in cash in her dresser at home.

Reidenbach's disappearance was discovered at 4:55 p.m. when her mother came to Mel Den to see her. One of Reidenbach's six siblings was paralyzed and in the hospital at the time and her mother wanted to know if Reidenbach wished to visit her. She ended up going to the hospital without her. Reidenbach's brother later came to the store as usual to drive her home, but he never saw her. Her mother called police later that evening after Reidenbach did not arrive home.

Investigators do not believe Reidenbach ran away. She left all her belongings behind and was not having any personal problems at the time of her disappearance. Her family describes her as a streetwise person who would not be likely to go anywhere with a stranger; they believe she was abducted by someone she knew and trusted.

Police questioned several people in Reidenbach's disappearance, including her boyfriend, who has passed a polygraph and was ruled out as a suspect in her case. Reidenbach's family has also been ruled out as suspects in the investigation. She is described as a responsible teenager who was devoted to her hospitalized older sister. Her case remains unsolved.

Some agencies state that Reidenbach vanished from Evans City, Pennsylvania.