Spahn was last seen on Sinsinawa Avenue in East Dubuque, Illinois at approximately 2:00 a.m. on February 11, 1975. She had left a bar beforehand and is believed to have been headed for a party. She was accompanied by an unidentified Caucasian male at the time; the individual is described as approximately 26 years old, 5'9 tall with wire-rimmed eyeglasses and full moustache. Spahn has never been heard from again.

In 2005, Spahn's case received attention when authorities checked to see if her remains were buried under the swimming pool at the Best Western Dubuque Inn in the 3400 block of Dodge Street in Dubuque, Iowa. The establishment was being demolished and investigators stood by to make sure there was no sign of Spahn's remains. The pool area was excavated down to five feet, but no evidence was located and Spahn's case remains unsolved.