7-Stud ruling question

[Jeffage]

What about this situation? I was playing in AC awhile back and bluffed the river against one opponent with four hearts on board. He thought and called, simultaneously mucking his board and holding all his cards in his hand like he was ready for a Go Fish game. Then when I showed, he rolled over a straight. Obviously, I didn't say anything since I'm not trying to win a pot without the best hand in a showdown, but curious if these same thoughts apply here or only turning your board down in response to a bet is considered a fold.

Jeff