Heist was last seen on the morning of February 8, 2002 when she took her children to school in Lititz, Pennsylvania. Her car seen by neighbors parked in front of her home in Lititz at around 8:30 a.m. Heist's husband says he spoke to her by phone from his workplace just before lunchtime, and she did not give any indication that something was amiss during this conversation. She has never been heard from again.

When Heist's two children arrived home from school on the afternoon of her disappearance, their mother was not at home. There were pork chops thawing in the refridgerator and laundry piled at the house. The children called their father, who left his workplace at 5:00 p.m., came home and called the police to report Heist's disappearance. By this time her car, a white 1998 Mercury Mystique which belonged to her employer, was gone from the driveway. There were no signs of a struggle at the residence and authorities initially believed she had left on her own. They now believe her disappearance was not voluntary, however. Heist left behind all her belongings, including her eyebrow pencil, which she normally took everywhere.

Four days after Heist vanished, her car was found legally parked in the 100 block of north George Street in New York City, New York, about 40 miles from Lilitz. The keys were missing and there were no signs of damage to the vehicle. The Mystique was found near a bus station, but authorities could not find any records that Heist had taken a bus or airplane anywhere. Her loved ones can think of no reason for her to go to New York City.

Heist and her husband were in the process of a divorce in 2002. She had taken two days off from her job to look for a new home for herself and her two children. The divorce was described as amicable, and it was finalized two years after Heist's disappearance. Her husband has since remarried. In 2009, he had his ex-wife declared legally dead.

Heist is described as a dedicated parent who would have never abandoned her family voluntarily. Her case remains unsolved.