Switchbox by Mickael Chatelain - Trick

Would you like to travel in time? How many of you would like to do it? How can a card, visible from the beginning, be the card that the spectator will select in a moment? A total mystery, as the spectator's signature proves that there is no switch or duplicate of the card. The card visible from the very beginning is indeed his card! Here, word for word, is the routine that you can present as soon as you receive your SWITCHBOX: Take a deck of cards from your pocket. Call attention to the folded card on top of the case, held in place by an elastic band. Remove the deck from the case, and hand it out for shuffling and examination. It's a normal deck. Invite a spectator to take any card from the deck and sign the face. The card is lost in the deck. Ask your audience how long they think it will take you to find the card. Explain that to make the challenge even more difficult, you'll put the cards behind your back. Finding a card without being able to see the deck would be impossible, no? Yo