A question for the rules/etiquette mavens,, I couldn't find a thread for this. Please redirect.

The 2 seat, UTG, received his 2d card, which hit his hand and obviously flashed. I'm in 4 seat and saw it clearly.

Before I could speak, dealer completes dealing and asks if i saw it and I say yes.. without id'ing it.

2 seat turns over card, dealer gives new card, player looks and snap folds. - all in what seemed like 2 seconds.

But player had somehow turned over his first card. I clearly saw JS. He turned over 4H.

(after the hand, I confirmed with him that he had the JS)

So he was out of the hand, my hand was unplayable ; I said nothing more- no harm, no foul.(I guess)

But it raised the question: if it all hadn't happened so quickly ( or if I were quicker on the uptake),
I 'm assuming I should speak up that it was the wrong card,

Then what happens? What if player calls or raises? What if I have a playable hand or a good hand?
Do I need to say something more?

He's cheating.

Speak up. "Hey, that's not the card that flashed."

Exactly. You should say something no matter what. If he folds or not.

Thanks for reply. Actually , it never occurred to me that he might have deliberately turned the wrong card.