The Strange Disappearance Of A Complete Deck Of Cards

We've all witnessed a magic trick where a chosen card disappears from the deck. Here's one with a difference.
The magician freely displays a deck of cards encased in its packet.
One card is shown and placed in with the rest.
The packet is now slid into a plastic case, and on the magician's command the whole DECK of cards disappears! The card displayed earlier is found elsewhere.