Take a look at your Wire Receipt or what ever wire agreement/instructions you had the customer sign.
Our says in bold... right up top...
The originator requests payment to be made to the beneficiary or account number named below: To the extent not probibited by law, the originator agrees that this wire transfer is irrevocable and that the sole obligation of the institution named above is to exercise ordinary care in processing this wire transfer and that it is not responsible for any losses or delays which occur as a result of any other party's involvement in processing this transfer:
If they wrote out a legit check to John Smith for $14,000 then John came over happily to cash his check, money out the door, but then your customer found out that John Smith ran a shady business would you give them their money back? How is that your fault?
The Bank acted upon the customer's instructions and if you all acted responsibly then you shouldn't be held responsible.