Kiefer was last seen at her home in the 500 block of south Hoffert Street in Fountain Hill, Pennsylvania on March 22, 1994. Her husband woke up and went to take a shower, leaving Kiefer asleep in bed. When he came back into the bedroom, she was gone. He assumed she'd left in the family's car, since it was also missing. Kiefer has never been heard from again. Her medicine and one or two of her jackets disappeared with her. Less than a day after her husband reported her missing, her car was found in Bethlehem City, Pennsylvania. It was parked illegally on Millside Drive, near Saucon Park, below a railroad trestle spanning Saucon Creek. There was no sign of Kiefer at the scene, and no indications of foul play. The car's seat was adjusted for a driver taller than Kiefer.

Bryan Steckel, a former neighbor, confessed to raping and strangling Kiefer in 1995. He was on death row in Delaware at the time; he had been convicted of murdering another neighbor, a pregnant woman. Police later determined Steckel's confession was false. He was executed in 2001.

Kiefer had been largely homebound for about eighteen months prior to her disappearance, due to her health problems. Her children didn't see any indications that she was planning to leave. Her husband stated there were no problems in their marriage. He divorced her in 1998, four years after her disappearance. They had been married for eighteen years by that time.