Ridinger was last seen on September 2, 1977. She left her job at the Rainbow Restaurant to hitchhike from Sherborn, Massachusetts to Cape Cod, Massachusetts.

For many years, the restaurant was the last place anyone reported seeing her, but in 1986 a witness came forward who said he gave Ridinger a ride early in the morning of September 3, the day after her disappearance. The witness, an elderly man who is now deceased, said he'd been en route to the Cape when he was stopped for a violation at a rest area at the intersection of Route 128 and Route 109 in Westwood, Massachusetts. The state trooper who stopped him had Ridinger in the backseat of his car, and asked the witness to give her a ride to the Cape. He said he dropped Ridinger off at the Hyannis Rotary, near the airport, and last saw her walking towards a nearby restaurant.

Ridinger has never been heard from again and the witness's account has not been confirmed. Her case remains unsolved.