PUF is the perfect finale reveal for a "signed card" routine!
The spectator's card is signed and then lost in the deck. Break the button off of your shirt. The button will find the card ... but how? Return their attention to your shirt and the button is back on the sirt. AND The signed card is attached by the button to your shirt!
A bizarre and unforgettable ending for your ambitious card routine!
You supply the real signed card as part of your own routine.