Answer:
Your bank or its customer can contact the bank on which the checks purport to have been drawn in an attempt to gain some information. It's likely that your bank would have a better chance at success in that effort. But the bottom line is that, assuming the return of those checks was timely, you had no option but to charge them back against your depositor's account. Legally, this is a matter between the check-cashing business and whoever defrauded it. Although you may feel the bank should try to assist, there is no legal obligation to do so.