I forgot to return the paper of the hotel room card to the hotel.

You can do without a deposit. If there is a deposit, it needs to be returned to the hotel.

If you stay in the hotel with zero deposit, there is not much problem in your hands. Try to have time to return it to the hotel. If you have paid the deposit, but you have the room card, try to communicate with the front desk to refund the deposit first, and then get the deposit when you check out the card.