Receiver makes a catch near sideline (clearly 2 feet in and possession) and gets pushed out of bounds and lands on ground, after contacting ground ball comes loose. The LJ had it as a catch, the FJ ruled it incomplete because he thought he saw a juggling of the ball while receiver was in process of catching it and they ruled it incomplete for that reason. TV guys went nuts claiming 2 feet in bounds etc, irrespective of that do we have a completion based on the ball coming out after receiver hits the ground out of bounds? I could not find a definitive AR on this and have gotten split opinions on this.
Nearly all catch/no catch plays are of the "had to see it" variety. No one has a better view than the officials who were there on the field; the odds are really quite good that they called it correctly.
Next, go back and read those two sentences again.

Having established that, here are some of the elements that go into making that judgment:
(1) If the player goes to the ground as he attempts the catch and/or due to a defensive hit just after the ball arrives, the philosophy that has trickled down from the NFL is that he must "survive contact with the ground" - meaning that if the ground jars the ball loose in this situation, the recommended judgment is that the player did not have sufficient possession for it to be a catch.
(2) If the player is juggling the ball, he must secure possession before touching OOB. If he is falling when possession is secured, see point #1.
(3) If the player has clearly established possession inbounds (this is purely a judgment call and is where guidelines like "make a football move" come into play), then it's a catch and the ball coming out after the hit and fall OOB is irrelevant.