Is it possible that you had a wizard quest buff that expired after the 15th quest? Because if you did the 15th and then it expired before you were able to do a 16th quest, you'd not get the 50 pt token.

You can file a ticket to get the 50 pt token. I just did mine to test and I got the token on the last quest so I am not sure if it was a site hiccup or maybe the buff that messed things up.