Ask your spectator to shuffle the cards. Have the spectator select a number between 1-10. With chosen number in mind, have the spectator count out two piles of face down cards equal to their chose number. Two piles of 5,6, etc. Now have the spectator select a pile. Have them reshuffle their chosen pile and place their favorite card face down on the bottom of their chosen pile. Now ask the spectator to place their chosen pile face down on top of the large pile.
Explain you are going to divine the cards remotely by having the spectator deal the cards. Ask the spectator to deal the cards one at a time face down into a pile on your command. Deal, deal, deal… do this 11 times. Once you’ve hit 11, say, “Ok we’ve obviously gone past your card” Place this newly counted pile face down on top of the large pile. Then ask if the spectator, “You’re holding all of the cards right?”. They will say no and reference the orphaned pile left from the beginning of the trick. Ask the spectator hesitantly to add the last pile face down to the big pile there by consolidating all cards into one pile.
Now tell the spectator you’re going to use a magic spell to find their card. Have the spectator spell out “This is my card.” Place a card from the pile face down for each letter. T-H-I-S-I-S-M-Y-C-A-R-… on “D” (the 12th card) have them flip the card over and it will be their chosen card.