Diane left her family's residence in Kennewick, Washington on June 18, 1985, to visit friends in Seattle, Washington. She joined a 21-year-old friend, Molly A. Purdin sometime during the day and both females were last seen in King County, Washington in the late afternoon hours. Purdin's body was discovered nearly one month later July 1985, off Index-Galena Road near Milepost 8 in King County. She was a victim of homicide. There was no trace of Diane and she has never been heard from again. She was presumed to be a runaway until Purdin's remains were discovered. Foul play is suspected in Diane's disappearance due to the circumstances involved in her case. Her disappearance and Purdin's murder remain unsolved.