Forgot to sign a check?

-I'm working in a grocery store. I had a customer that wanted to cashed his third party check. So, I ran it to a certegy machine to get an approval, and it was approved. I just realized now that I forgot to ask the customer to sign/endorse the third party check and the check was already sent in the bank yesterday. In the front of the check, I have his phone number, driver's license #.,



now, I'm worried if the bank will not accept it because of no signature in the back of the check. and will return back to our store! I might get written up on this one..



I hope this is not really a huge mistake. :(