Check a Hand and Foot deal
Before a round is dealt, the app shuffles the deck and seals its order. The seal is on the table while you play. When the round is over, the Fair deal screen of the app shows the shuffle code.
Type the code here. This page shuffles again on your own computer, with the same shuffling program as the app, and shows the seal and every card each player was dealt. If the seal is the one you saw during the round, and the cards are the ones you had, nobody changed the deck while you played.
Nothing you type leaves this page.