Common sense tells me it was a catch.
But according to the "rules" there was some bobbling. Also, it was called incomplete on the field, so there would have to be INDISPUTABLE evidence to overturn the call (especially in a game of this magnitude).
If it was originally ruled a catch and fumble and Pittsburgh challenged it, I think they would have upheld the fumble. Just goes to show that there are still "gray areas" that the league needs to clear up in the rulebook.