We did notice immediately, but we had the first board to play following a grand speaker introduction, and we just went with it instead of resetting the board with all eyes on us and making the hosts look bad. Speaking for myself at least, I can't believe he didn't notice immediately too.
It made my noting down of the moves quite hard.
> I would have thought it as jarring as a mistuned musical instrument.
This was exactly my thought, how much it mattered to him at his level.