Mentalist offers to demonstrate what the difference is between a "magician" and a "mentalist". A packet of playing cards are shown to be all different. Performer demonstrates how a magician would perform a standard "pick-a-card" effect by mixing the cards, and then pantomiming how a card would be selected and then returned to the packet...mixing the cards again, and then revealing what the chosen card would be.
The performer states, "That's how a magician would do it"...Now here's how a mind reader would do the same thing". The packet of cards are placed on the table in full view. The performer tells the spectator "When I snap my fingers, name any number between #1 and 10". Immediately the cards are handed to the spectator, and one-by-one they are counted down to the freely chosen number. The selected card is shown to all, and the performer directs the spectator to look through all of the cards and verify that all of the cards are different; there are no duplicates.
Now, attention is called upon the wallet that has always been in full view. Without hesitation or fumbling, the performer shows that one "prediction card" has been in the wallet from the very beginning... an exact match to the spectator's card found at their freely selected number!