Zabel was last seen by her family in her hometown of Cedar Falls, Iowa on March 21, 1978. After she disappeared, a frozen chicken was found thawing in her kitchen sink; it was meant to be for her family's dinner. Zabel has never been heard from again. The day after she was last seen, her vehicle was found at Black Hawk Park with her purse inside. She enjoyed taking walks in the park. Authorities theorized she either fell into the Cedar River by accident, or intentionally drowned herself. She had been under treatment for depression, but her psychiatrist told authorities she had shown marked improvement in the months prior to her disappearance.

There is no evidence that Zabel left of her own accord. Her credit cards were never used after she disappeared, and she did not have sufficient assets to sustain herself for very long. She left behind a husband and three children. Zabel worked as a teacher's aide at River Hills School in 1978. She was declared legally dead seven years after her disappearance. Her case remains unsolved.