Landsdell was last seen leaving her boyfriend's Belen, New Mexico house at 2:00 a.m. on September 21, 1985. She was en route to her apartment on Jarales Road, but it's unclear whether she ever arrived there. She has never been heard from again. After her disappearance investigators found her apartment door open, but nothing inside was disturbed. Landsdell's 1978 Porsche was found at an apartment complex in Albuquerque, New Mexico in February 1986.

Landsdell got divorced a short time before her disappearance. She had started a new nursing job in Lovelace, New Mexico. Foul play is suspected in her disappearance, which remains unsolved.