There's 2 things you can do..
1. Tell your husband that you thought it had been cancelled and that you don't know why a card has been sent. The card will not have any information about outstanding money, that will only show on your statements, so that's another problem ie trying to stop husband getting to the post before you.
2. It's a tangled web we weave....tell him the truth....he may go mad but if he is a good husband a loves you he will calm down and maybe help you to sort it out. Telling the truth at least will take months of future worry off you.
Best of luck.