Did you pay by check or Paypal? If it's snail mail, it just may take a little time for Joe to receive the check. If it was paypal, drop Joe Gardner a PM. Well... drop him a PM in any case and let him know that you've paid anyway. Also, did you make sure he knew what your user name was so he knows which member gave the donation?
I reiterate- send Joe a PM (Joe Gardner) and let him know your story. He can update your account for you.