Shinn was last seen on July 20, 1978, in Magnolia, Arkansas. She owned an art studio and was trying to sell a house on East McNeil Street. On July 19, she showed the house to a man who proposed a land trade, but she doubted it would happen. The next morning, he called again and they agreed to meet at the EZ Mart near her studio to view the house.

A witness saw Shinn with a man matching the description at the house around 11 a.m. A young girl also saw a man at the EZ Mart at that time making a phone call. Shinn was never seen again.

That afternoon, her blue 1976 Buick Special was found at Smitty's Grocery with the keys inside. Her purse had been emptied on the floor, her sneakers were under the pedals, and her wallet was still in the car, but her address book was missing. The car showed signs of being driven through a field. Police believe she did not leave voluntarily.