my friend did a card trick which has me beating my head trying to figure it out. he spread out all 52 cards on the floor and said to pick one up and look at it after he left the room and then to put it back. when he came back into the room he took my hand and pretended to smell it. over the next few minutes he eliminated cards one by one until he narrowed it down to a few cards from which he withdrew the card I'd originally picked out. this was my deck. it was unmarked. no one else was in on this trick. how did he get that card?