PAC12 reviews itself and finds itself clean.

[EagleMountainUte]

On third-and-goal from the 3-yard line with 17 seconds left, Ole Miss quarterback John Rhys Plumleerolled to his left and connected with Elijah Moore near the goal line. Moore’s feet were in the end zone, but the official on the sideline nearest the play ruled that the ball did not cross the plane, and the ball was spotted just short.

Espn article

Feet in the endzone but can’t see the ball I guess???

[Larry B]

Both feet in the endzone, ball placed on the receivers hip. But the ball didn’t cross the line?

Yeah sounds right.

[salty-ute]

I think the ref did a spectacular job on this one. I saw a fan video that was taken from the opposite side of the goal line. You couldn’t ever see the ball cross the plane. The receiver left his feet from the endzone, caught the ball in the air and landed on a knee with the ball likely short of the goal line… Too tough to tell even with the video, it’s really hard to be critical of a referee there.

[Calgradutedad]

Ol Miss coach was hoping for a bailout on his poor clock management.

[UTE98]

Run the route a yard deeper or got to the guy in the back of the end zone and there is no question. Don’t run a route short and expect the refs to bail you out. I can see a few reasons why they may have ruled this not a TD.

1. The ref does not believe the receiver has possession in the end zone, establishes it after leaving the end zone.

2. The ball never crossed the plane of the end zone.

3. A comeback route out of the endzone is not the same as a route going out through the endzone so is a bigger risk IMO.

I think they probably should have reviewed the play, but you can’t rely on the refs to bail you out as @CalGradUteDad says for poor clock management. Otherwise you’d see end of game routes with about :01 on the clock to the sideline in hopes of getting that extra second.