Heads up for everybody else and I have filed as a radar: 28283019
A user has reported that after updating my iMessage app, the app icon has disappeared. He has tried swiping right through all apps, looking at his Manage list, force quitting iMessage, rebooting his phone. Can't find my app. When he received a game message from someone, it directed him to download the iMessage app. My app page says it's installed on his phone.
I am trying to solve this by pushing an external TestFlight build out to him to see if iMessage puts the app back in his tray. Will report back.