Switalski was last seen in Chicago, Illinois at 10:15 p.m. on July 15, 1963. She attended a carnival with friends at St. Priscilla's Catholic Church that evening. She has never been seen again. Her parents received a letter from her two days after her disappearance, however; Switalski wrote that she was fine and would be sending them some money soon. She said she was "experiencing a strange but educational experience." She wouldn't tell where she was because she didn't want anyone to "interfere," and she added she might never see her parents or friends again. The letter was postmarked Oak Park, Illinois, a suburb of Chicago.

Switalski never got in touch with her family again. Her parents didn't know why she ran away and weren't aware of any problems in her life. She was a good student who had just completed her junior year at Notre Dame High School, and she had put a deposit down for her senior yearbook and class ring. She had a job at a neighborhood story and also earned money babysitting.

It has been established that, following her disappearance, Switalski joined an organization that sold magazines door-to-door. It was bound for California at the time. When questioned, the couple who ran the group admitted they had hired her, but gave conflicting statements as to what happened afterward that. The wife said Switalski had left the group sometime before; the husband claimed she had never left Chicago at all. Switalski's disappearance remains unsolved. There has been no indication of her whereabouts since 1963.