If you, the employee, report the loss or theft before the card is used by a third party, you cannot be held liable for unauthorized charges made by the third party. Also, if an unauthorized third party makes charges on the card before you can report it lost or stolen, the most you will owe for the unauthorized charges is $50 per card.
These limitations on your liability apply only if an unauthorized third party uses your card. If you use the card in an unauthorized manner, you are responsible for all charges.