Two cards are selected by two spectators.

One card is signed across its face.

Both cards are now lost in the pack.

You take out your wallet and show money inside.

If you fail to get the two cards into the wallet you
will share the money with the spectators.

At random you take one card from the pack and place
it in the wallet and hand wallet to first spectator.

He is asked to take the card out of the wallet and it is seen to be his.

He then closes the wallet and in its empty state he passes it to the
next spectator who places it still empty into his pocket.

You explain that somewhere in the deck is the signed card.

When you spread the deck the signed card has vanished.

Surely it can't be in the wallet as the empty wallet has been placed
in the spectator's pocket by the spectator himself.

However when the spectator takes the wallet from his pocket
and opens it the signed card is indeed inside the wallet!