Hansen was last seen in King County, Washington on August 10, 1962. She planned to meet her sisters at the World's Fair in Seattle, Washington, but never arrived. She has never been heard from again. Her car was found abandoned several days after her disappearance, with no signs of foul play and no indication of Hansen's whereabouts. An extensive search of the area turned up no sign of Hansen, and a private detective her parents hired was also unable to locate her.

Hansen left behind a young son who is now an adult. For years after her disappearance, there were rumors that her body was buried beneath a local barn. The barn had a new concrete floor poured around the time of Hansen's disappearance, replacing the old dirt floor. The barn has since been demolished and is now a road. In 2006, at Hansen's son's behest, investigators examined the road with ground-penetrating radar. No evidence was located, however. Hansen's case remains unsolved.