Check the card opening record and see if you can find the owner of the card that was swiped by the thief.

If you find it, go directly to the dormitory to find someone else.

Don't ask him if you will lend the card to others yet.

You can find any excuse to borrow his card or something.

If he answered, the card was not here, so he lent it to someone else.

That would be easy for you.