....since I was there, and since when I saw the ball hit the ground there, I thought "Did that hit his foot? Looked close."
What happened there, and it probably didn't make TV because it was on commercial, was that the referee called the ball down where it was downed. Then the side judge, the only one that apparently noticed it, went RUNNING up to the head referee pointing back to the spot where he thought the ball hit the player. There was some jawing between the two of them, then the head ref made the announcement and respotted the ball, at which point Mullen went apeshit and called for the challenge.
So yes, while the Sun Belt replay official confirmed it incorrectly, the call was originally made correctly, until interfered with by the side judge, whom I might add was employed by the Southeastern Conference, the gold standard in football officiating.
Also worth mentioning was that while this was going on, I was talking to an MTSU fan whose dad used to be an SEC ref and is now an NFL ref. The guy said you'd be surprised how few former SEC refs there are now in the NFL. Apparently they are not thought of well at the next level at all. He said most of them come from the Big Twelve, the Big Ten, and the Pac 10. Very few from the SEC.