"I'm just overwhelmed," Thorns said. "My dream came true. It was a dream for me to do this, to beat these guys."
The Horned Frogs hadn't led since the opening minutes of the game when Thorns started overtime with a layup to break the 85-all tie, and they didn't give the lead up. Thorns made his eighth three-pointer with 1:21 left, dribbling through several defenders and shooting over another one to make it 96-91.
Thorns, a Las Vegas native who first went to Virginia Tech before going to TCU, led five Horned Frogs in double figures.
Mike Moser had 22 points and all five starters scored in double figures for UNLV (22-5, 6-3).
TCU had a chance to win the game at the end of regulation after Oscar Bellfield had a turnover, but Thorns made one pass too many.
Kyan Anderson stole the ball and got it to Thorns, who was driving toward the basket. Instead of taking the shot, he dished it to J.R. Cadot, who made the layup - except the clock ran out before the ball got out of his hand.
Cadot had 17 points and 16 rebounds for TCU.
Marshall and Chace Stanback each had 17 points for UNLV.
In other games *
At Clemson, Andre Young and Tanner Smith scored 13 points each and the Tigers held No. 22 Virginia to its lowest point total this season, 60-48.
The Tigers (13-12, 5-6 Atlantic Coast Conference) took control with an 18-9 run over the final 8 minutes to give the Cavaliers (19-6, 6-5) their second straight loss. Jontel Evans led the Cavaliers with 17 points.
* At Alabama, Patric Young scored 19 points and No. 14 Florida (20-6, 8-3 Southeastern Conference) beat the Crimson Tide, 61-52. Alabama (16-9, 5-6) has lost two in a row without top two scorers and rebounders JaMychal Green and Tony Mitchell, who are on indefinite suspension.
* At Minnesota, William Buford scored 24 points as No. 6 Ohio State (22-4, 10-3 Big Ten) defeated the Golden Gophers, 78-68.
* At Oklahoma, J'Covan Brown had 19 points and Texas (17-9, 7-6 Big 12) rallied from an eight-point deficit to beat the Sooners, 69-58.