Stephanie's mother gave her money for a snack and dropped her off at the Challis Bowling Alley in Challis, Idaho on October 11, 1993. She went bowling with friends, then departed at approximately 4:45 p.m.. She was last seen walking on Highway 93 towards Challis High School at approximately 6:00 p.m. that evening. The school was across the street from the bowling alley. Accounts differ as to whether Stephanie was going to the high school for soccer practice, or whether she was heading for her family's residence, about 500 yards away. By 8:15 p.m., she hadn't arrived home and her parents notified the police. An extensive search covering 7,000 square miles in two counties turned up no sign of her. A yellow pickup truck with red pinstripes was seen in the area around the time she vanished, and may be connected to her disappearance. Keith Glenn "Mark" Hescock has been investigated for possible involvement in Stephanie's case. Hescock kidnapped a fourteen-year-old girl from outside her home in the early morning hours of June 5, 2002. He had known her family.

The girl was able to escape that afternoon when he went to work, leaving her chained to a bed in his home. When the police attempted to arrest him, Hescock fled in his vehicle and lead them on a forty-mile high-speed chase, which ended at a dead-end road in the Big Hole Mountains. There he shot and killed a police dog, shot and wounded an officer, and then committed suicide. He owned a yellow pickup truck similar to the one that may be connected to Stephanie's case, and Stephanie's great-grandparents believe he was the "weird guy" with a yellow pickup truck who camped next to them when they went camping near Twin Peaks, Idaho the weekend before Stephanie went missing. Authorities have not been able to link Hescock to Stephanie’s disappearance. Authorities have five to ten persons of interest in Stephanie's case, none of whom are family members. Investigators believe Stephanie was taken against her will by a stranger. Her case remains unsolved. She has brown hair and blue eyes. Stephanie has a cowlick on the right side of her hairline and a scar near her right eye. She has a space between her two upper front teeth. She was last seen wearing a maroon and white-striped hooded sweatshirt with "GIMMIE" imprinted on the front in white lettering, maroon sweatpants and maroon and white shoes.