Fortune-telling sketch

Does the fortune teller know your last name?

He has a stack of cards, each with N surnames neatly arranged. He will make you draw a card with your last name without looking at it and give it to him. He will sort out a pile of cards, pull out the card with your name on it and ask you if your last name is on this card. Finally, measure your hand and pretend to work out your last name. To put it bluntly, it's as crooked as magic guessing poker.