The Ref is not sworn to secrecy, there's no player/ref confidentiality. It is the player/team's responsibility to be clear with the refs with their intentions. The announcement was made public over the PA system and a Lions player, coach or assistant should have caught that if it was not correct and corrected the ref or at worse they would have had ample time to change their playcall in the huddle. It's the refs responsibility to make the correct call, but it is the team's responsibility that the ref understands their intentions.
What the Lions had here was