Marquez was last seen at her home in Bell Gardens, California on September 13, 1983. She tucked her two daughters into bed that night. When her daughters woke up in the morning, Marquez was gone and they were alone in the house. She has never been heard from again. Her husband said she ran away with another man. Marquez and her husband were separated and in the process of a divorce in 1983. Their oldest daughter, who was five years old when her mother disappeared, describes her father as abusive and volatile. Shortly after Marquez's disappearance, her husband went to Mexico, leaving his children to be brought up by their grandmother. He remarried there and had two more children. He died in 2007.

Marquez's disappearance remains unsolved. Her children believe she was murdered by her husband.