Peter opens his eyes and opens his mouth to tell Gabriel to go fuck himself, because obviously he's full of shit and this just doesn't work. The question gives him pause, though.

Shit. Shit, he went and got turned down in Jerry's basement. Fuck. Suddenly no, he's not 100% sure he's still 100% human, even if the stake blessed by St. Michael had seemed to turn all of them human again. Would that mean angels don't hear him pray anymore? Because that is seriously fucked up.

All this flashes through his head pretty quickly, but there's still a longer pause than there should be, and Peter's expression shifts for just a moment or two before he asks, in his best annoyed voice, "Are you sure you're an angel?"