ANY card is selected from a regular deck. The card is returned, you show the top card say 4C, they state that this is NOT their card. Give them this card to hold. A second card is shown say KH and placed on to the face of the deck, this is also NOT their card (not your day). Visually the KH changes into a card with the words LOOK IN YOUR HAND printed on it. They now look in their hand to see they hold the SELECTED card!
Card visually changes to read Look In Your Hand Spectator is shocked to see they are holding selected card!