By the way, and this can happen -- it happened to me twice -- the spectaor calls out a card they didn't actually see. My way of responding after I have cut the deck is to tell them, "I apologise! When I was separating the cards the thought just popped into my head of the (name one of the two cards you cut to)", and then reveal that card, and say, "And here it is." It's a great save, because while you didn't cut to the card they called out, you did somehow cut to the card that you were "thinking of" and it's still a magical moment!