I'd say chances are, your customer was the victim of a Craigs List or EBay overpayment scam.
Craiglist scams Since the amount exceeds $5,000, if you can identify a suspect (i.e. the recepient of the funds your customer wired) file a SAR on that individual and list your customer in the narrative. If you conclude that your customer knew that the check was fake and cashed it anyway, then file on your customer.
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