The last time ZOS had a promotion like this you just had to make sure you did the thing in the time window (generously within the window ideally), and wait for the dispersement of the rewards. If you know you did the thing in the time window and don't get the rewards by the dispersement date, submit a ticket to ZOS and you should get it that way. Other than that there hasn't been any verification that you will get the rewards prior to actually getting them to my knowledge.