Ryan Woolridge grabbed the defensive rebound from Lockett's second shot at the line, but then missed a layup to end it.
Trejon Jacob and Michael Douglas scored 14 points apiece to lead FIU (12-16, 6-9 Conference USA). Lockett finished with 13 points.
Woolridge scored 18 points and Tope Arikawe chipped in 12 for North Texas (14-14, 7-8).
Tope Arikawe made two free throws and a dunk, Roosevelt Smart hit a 3-pointer to cap a 9-0 run and the Mean Green led 67-66 lead with 3:48 remaining, but after that they made just one free throw.
FIU didn't fare much better late. Lockett made just one field goal with 2:51 left before hitting the game-winning free throw to snap the Panthers' three-game skid.
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