Pfeifer was last seen in Katy, Texas on April 12, 1986. She lived with her parents there. She said she was going to a party with five other people. The party was on the outskirts of town, about ten miles from Pfeifer's parents' home. Pfeifer never returned home. She had a history of dropping out of sight for short periods; as a result, her parents didn't report her as a missing person for four weeks.

Witnesses at the party said Pfeifer became extremely intoxicated that evening, which is typical of her behavior. They said she left with a man at around midnight. Police identified and questioned the man Pfeifer left with, and he said he knew nothing about her disappearance. Years later, while in prison, he was questioned again and admitted he left the party with Pfeifer. He said they went to his apartment in Houston, Texas and used drugs there, then he drove her back to Katy. The man said he stopped to get gas at a gas station on north Mason Road and, while he was filling the tank, Pfeifer left. She got into a brown pickup truck driven by a person she appeared to know. She has never been heard from again. The man subsequently passed a polygraph test about Pfeifer's case.

Pfeifer didn't take her purse, identification or money with her when she disappeared. Investigators initially believed she left of her own accord, but they began to look into other theories as months and years passed and no one had heard from her. Her case remains unsolved and foul play is suspected.