Just a guess but I bet the offense was big either hitting someone and not stopping or possibly riding on someone else's pass. Making them walk down is not a bad punishment. My guess is they told him that to get the board back he has to show up in a managers offense for a chat. I don't think they could just keep it. I recall something along this line happened at Whiteface during Bruce's time as GM and that is how I heard it played out.
if You French Fry when you should Pizza you are going to have a bad time