I received an email this morning notifying me (as administrator) to assign credit cards. However, in review of the cards to assign, some of these cards have previously been assigned to the respective user who has used the card, made transactions on the credit card and has submitted expenses of credit card transactions.

What would be the reason I would need to re-assign a credit card to an employee? Is it possible a credit card can 'unassign' itself from the cardholder in Concur which would require re-assignment?