I noticed the No Longer Grinchy hat:
It clearly says: (emphasis mine)
participate in successfully reopening or undeleting a question
I have reopened several questions today, latest is this one, using the Dupe Hammer, however I wasn't given the hat. Why is this?
All the questions I reopened so far were then closed again, I did it as a cleanup process to remove the embedded markup of old duplicate closure, and put the notice in place instead.