I see what happened here. It has to do with not completing the goal that awards you the unseeing. You get progress on the goal when you finish heroic but your guild isn't done yet, you go to bed and the event ends as you're sleeping and the goal disappears as intended, you wake up and get the guild prize for heroic but the goal for the unseeing is already gone and therefore can't complete and award you the unseeing.
Quite a system Gree has, next time set an alarm at night to wake up before the event ends and you'll be good.