Partridge left her classes at Ferris High School in Spokane, Washington at 12:30 p.m. on December 4, 1974, because she felt was suffering from cramps. She was unable to find a ride and decided to walk the two miles to her home in the 5400 block of south Custer Street; she felt walking might help her feel better. She was last seen walking south on Havana Street near 37th Avenue. There were reports that a green Pinto station wagon was in the area at the time, possibly following her. Partridge never arrived home and has never been heard from again. Her parents reported her missing when she failed to report for work at the Lincoln Heights Theater.

Partidge's father had bought her tickets to a Beach Boys concert which took place after disappearance, and the police went to the concert to see if she would arrive there. They did not see her. It was later determined that Partridge's tickets were in fact used, but authorities were unable to find out who used them. Partridge was carrying a brown leather purse with a blue flower design and a braided shoulder strap at the time of her disappearance. The contents of the purse were located in the area where she was last seen on December 6, 1974, two days following her disappearance.

Authorities initially believed Partridge left of her own accord, but her family never believed this, and police have since revised their opinion; they now think she was taken against her will. She and her 20-year-old boyfriend were hoping to marry and were planning to select an engagement ring on the day of her disappearance. She worked for her high school newspaper and was on the school drill team. Partridge is the oldest of five siblings. She had moved to Spokane from California just a few months before her disappearance, and had said she would like to return.

In 2011, investigators announced they had a new witness who may have seen Partidge during her walk home. Authorities haven't disclosed the witness's identity, but stated the person allegedly saw Partridge at 4:15 p.m., several hours after the last confirmed sighting of her. A Caucasian male in his forties or fifties, as well as a white truck with a dark-colored door and a van back end, were nearby.

Three suspects have been questioned in Partridge's case over the years, but no one has been charged in her case. Her fiance was questioned extensively but never named as a suspect. Her parents got a divorce after her disappearance, but later reconciled and remarried each other more than ten years later. Partridge's mother died in 2004, but her father is still alive. Her case remains unsolved.