The AR is basically a unicorn. I have never seen an instance where everyone gives up on a play with a ball in an endzone and there is no whistle or signal.
Bill Lemmonier had a video he shared a while ago with the AR happening on a busted 2 point conversion return in a game in Mexico (yes, seriously).
There have actually been a handful of these plays (potentially) where the ball carrier has nothing but green grass in front of him and he drops the ball at the 1 yard line. 9/10 times the covering official rules TD, so the replay case book comes into play (essentially an inadvertent whistle).
I do believe that if the on-field official correctly rules the ball was fumbled prior to going in the end zone, drops his bean bag and makes no other signal to kill the play, and nobody recovers, and they eventually rule TD due to the ball being abandoned, then I think replay would have to stick with that call. The case book play shows them correcting an error in judgment (Official ruled TD when it was not).