Herbster left her new job at an electronics firm at 4:00 p.m. on March 9, 1979. A co-worker dropped her off in Westampton Township, New Jersey, within two miles of her Mount Holly, New Jersey home, so she could walk the rest of the way. Herbster was last seen at 5:15 p.m. while en route home. She never arrived has never been heard from again. She is not believed to have left of her own accord, as she left personal items behind at her home. She was, however, carrying a large reddish-brown suede shoulder bag with a zipper across the top.

After Herbster's disappearance there were persistent rumors that she was murdered and her body dumped at a local construction site. Police were never able to substantiate the stories, however. Her case remains unsolved.