Effect: You produce two red backed cards each have a keyhole.
Invite your spectators to inspect them. Nothing to hide!
Your two cards are placed in full view on the table.
A spectator freely chooses and signs a card.
The card is lost in the Deck.
Take your two cards and place them on top of each other.
Everything is completely fair.
Shake the cards gently. The spectator will see a card materialize between them.
A mind blowing appearance!
Invite them to turn over the card themselves.
They will see that it ACTUALLY is their card -- the signature proves it!
Let them keep the card as a souvenir.
End clean, everything is examinable!