Given that this play was specifically told to the officiating crew BEFORE the game, Campbell probably figured they would do their job and get it right.
Also, I just re-listened to the broadcast and I didn't hear it announced at all. Not saying it wasn't announced but I was specifically listening for it and I didn't hear anything. If I couldn't even hear it when I was listening for it, I suspect it would have been super easy to miss it if I wasn't.