Blumhorst was last seen leaving her place of employment, the Super Value grocery store in Mendota, Illinois, at 1:07 a.m. September 20, 1990. She worked the night shift. She was recovering from an illness and decided to leave work early and go home to sleep. She has never been heard from again. Blumhorst's blue Chevrolet Corsica was found parked in her garage at her home four blocks away the following morning. The garage door was closed and there was no sign of her at the scene. At the time of her disappearance, she resided with her parents and younger brother in the 1200 block of Monroe Street.

Investigators do not believe Blumhorst left of her own accord, as she left behind all her clothing and her vehicle. She had no credit cards and her bank balance was only $4 when she disappeared. Authorities theorize that, after parking her car at her home, Blumhorst got into another vehicle with someone she knew. A year after her disappearance, investigators searched a residence belonging to the father of a man Blumhorst had dated. The boyfriend maintains his innocence and has not been charged in connection with her case, and no evidence was located during the search.

Blumhorst is described as a shy, retiring young woman. She was carrying less than $10 in cash on the night of her disappearance and she'd just rented a movie to watch. Her case remains unsolved.