Forged Endorsement on deceased payee

I had a customer contact me today saying that she had issued a check to a deceased payee (she didn't know he was deceased at the time.) The check has cleared the account and has an endorsement on the back that is clearly forged as the payee was already deceased at the time it was negotiated at the other bank. Since the payee is not able to sign a forgery affidavit, would it be sufficient to send a letter to the bank with a copy of the check, death certificate and something from our account owner stating that the check had to have been forged? I'm not sure how to handle this since the payee cannot sign? Thank you.

Check with your state probate laws to be sure, but I expect that the representative of the payee's estate would be tasked with the responsibility of filing an affidavit of forged endorsement claiming that funds were due to the estate from the drawee of the check.