Black Market by Gary Jones

EFFECT: Your spectator examines and signs one of your business cards - it's noticed that there is a little square of black paper stapled to the card. This is signed by them and left in their possession. Now, they choose a card which is also signed. You take that signed card and tear a corner off of it. That corner vanishes in the cleanest possible way, without ANY sleight of hand. You now turn your attention back to the signed business card they've been holding the whole time. You touch a flame to the little piece of black paper - it burns away in a flash and the missing torn corner spectacularly materialises in it's place, stapled to the business card! Of course, everything matches up and both the playing card and (more importantly) the business card can (and WILL!) be kept by your spectator.