So what happened to her?
The two main theories presented by the FBI, who entered the investigation on October 12, 1976, were the following:
1. Trenny was abducted and taken out of the park, likely taken at the place where Andrews Bald Trail intersects with the Appalachian Trail. She was then hidden someplace (possibly the fog-shrouded tower on Clingman's Dome) until it was safe to walk unseen to the spot on the road where the dogs had tracked her. From here she was taken out of the Park by vehicle.
2. Trenny, while walking ahead of her classmates, became lost. She may have followed the Appalachian Trail by mistake and made her way to the tower on Clingman's Dome. Seeing headlights, she made her way to the road. Instead of help, she was either abducted or met with some other kind of foul play.
Kelvin Bowman was a student at Bearden, a year older than Trenny. A few months prior to her disappearce, he and another student, Ronnie Joiner, broke into the Gibson residence one night. Hope Gibson, hearing the noise, got a gun and ended up shooting Kelvin in the foot.
Kelvin was arrested, tried and sentenced to time in a correctional institution. He had allegedly made threats to kill Trenny once he got out. Some of the students claimed that they had noticed Kelvin following the bus to the mountains that day by car. Frank Hall, Bearden High's principal refutes this, claiming that he was in class that day. Wayne Dunlap was adamant that no cars followed the bus and none of the students were aware of the destination of the bus prior to its departure.
Robert Simpson was a year older than Trenny and was a friend of Robert, Trenny's older brother. He had a car and he and Trenny often went for short rides together, to West Town Mall and other places. It is said that Robert was very fond of Trenny, but it is not known if they were ever a couple.
Trenny had shared a seat on the bus with Robert on the way to the Park that day. She was also wearing his heavy brown plaid CPO jacket when she disappeared. On the trip, it was Robert that she had spent most of her time with, and after she left his company to return to the bus, he claimed that he had gone tracking a bear.
Later some of the students on the trip had told Mr. Gibson that Trenny's hair comb was found in Robert's car. Trenny was known to never be without that comb, she carried it in the right hip pocket of her jeans. There is no record that this was ever investigated further.
On two occasions when the Gibson's were in the Park searching for Trenny, Robert Simpson came by the residence and told Tina Gibson (Trenny's younger sister) that "If Kelvin Bowman has Trenny, he will kill her. If he doesn't have her, I think she might have run off with some horny hitchhiker".