Until the whistle is blown, you can go after the puck, if the puck is anywhere in the crease and the ref has not blown the whistle, then you can go after it. It is incidental contact if Luongo got turned around. The definition of interference is making contact with someone when they do not have the puck. The puck was there. As stated before, the ref should have blew the play dead, but he didn't. Goal should have counted.
Incidental contact is still a goaltender interference. And the fact that this so called incidental contact was the reason for the goal is why it is a no goal.