Mirage Card Switch Frame

Magician shows a transparent frame with a small card inside
He shuffles the deck and asks a spectator say 'stop' for choosing one card.
A Heart J is selected from a deck and put on the desk.
He asks the spectator if he can still remember the card inside the transparent card.
It must be club 3.
But after the magician covers the card with his hand, the club 3 magically turns to Heart J.
The selected card on the desk turns to Club 3, not Heart J.