Shimkus was last seen in the Esplen section of Pittsburgh, Pennsylvania on December 20, 1972. She left her house in the 200 block of Oregon Street at 5:00 p.m. to walk to work. Shimkus was employed as a cook at the Rockwood Lounge in the McKees Rocks Shopping Plaza at the time. She has never been heard from again. She did not take any personal belongings with her.

The new owner found bone fragments in the crawl space of Shimkus's former home in 1995, but they turned out to be from an animal. Shimkus's husband died of cancer in 1965. In 1972, Shimkus lived with her daughter. Her adult son was married and lived elsewhere in Pittsburgh. Shimkus was on good terms with both of her children at the time of her disappearance and was considering marrying her boyfriend.

There are some indications that Shimkus is remained alive for an extended period of time after she went missing, but there have been no confirmed sighting of her since 1972. Her case remains unsolved.