If you've had a look at the mobile apps page or the page for your GH:L sticker, you've probably noticed a teaser for two other stickers. In case you hadn't, here's the bonus clue text:
Bonus Sticker Clue
Clue #1: Did you see something? Check-in with "panic button" when you're watching and don't forget to share what you saw in your comment and on the official website.
Clue #2: Ghost Hunters Halloween Live goes until 1am, so keep checking-in throughout the event to show that you're brave enough to watch through the end.
Sounds pretty straightforward, right? For the Panic Button sticker you need to check-in during the show with the phrase "panic button". For the other one, just check in during the last hour of the show. Looks like we're staying up late on Sunday!