Originally Posted by enjolras
Not what the rule says.
The key bit being that last clause. The rule says that if you go out of bounds you can't be the first to touch the ball, period. The reason the "re-established himself inbounds" is in the rule is that it distinguishes when the penalty occurs. If you go out of bounds and touch the ball without re-establishing in-bounds then the pass is simply incomplete.
You got the rule interpretation correct. It's just that the ref blew it and did not call PI. You're not simply allowed to just push a defender out of the endzone. I know they can bump within 5 yards of LOS and if they are close to the sideline that's fine, but I'm pretty sure you as a defender can't just push a player out of the endzone while he is running a route. That was a very badly blown no call IMO.