Answer:
Assuming that your stamp has verbiage along the lines of "Credited to the cccount of the named payee. Absence of Endorsement Guaranteed" all you are guaranteeing is that the check was deposited into an account owned by the payee of the check, in this case the business. This guarantee does not in any way involve the individual who brought the check in for deposit as the person at your teller window does not have to be an authorized signer of the businees to deposit checks.
First published on BankersOnline.com 6/27/11