Take a look/listen to the video included regarding the question. (it's long but quite interesting)
Player A hit quads on the turn, after exposing his cards to Player B with some chatter - then Player B throws his cards in the muck (with some theatrics apparently). And for whatever reason, the dealer decides to deal the river.

The question is, shouldn't the hand be over once Player B threw his cards in the muck? What do you think?

You Tube

definitely yes. If a player folds a hand, the hand is automatically won by the opponent, and the dealer's mistake is irrelevant in this case.

Once the cards hit the muck that is it. There is no retrieving the cards.

Interesting discussion in the video. Personally I do not see how anyone can lay claim to a hand they through in the well, regardless if it hits the muck or not, the persons action certainly sounds like he through the hand away

Once you mucked your hand, it's done, no recall!!

Once the cards are in the muck, those cards are dead. I have learned the hard way to always see they cards at showdown. If they announce they have a hand that beats you make sure to see the cards before you muck a losing hand. Some people will over state their hands hoping you toss a better hand in the muck to win the pot.

Once mucked and no one left in the hand the hand is over.

Nope. Not at all. Never!!
Once you fall off that tightrope there's no safety net. It's not golf where you can "mulligan."
Standing by your decisions adds character and zest to the game.. otherwise let babies play.
I usually leave at the first opportune moment when these types are at the table I'm at..trouble.

The guy tossed his had, he is out, period. You are responsible for your cards and your actions. If the dealer makes a mistake then there are some options.

Yeah, if the cards are tossed to the muck it's over, if the dealer didn't read the move correctly and made a mistake, that's another thing.

yes more agroo

I would say, something like 99.99% of the time, you should not be allowed to retrieve your hand from the muck after verbally surrendering. But I have seen some very unique situations in poker. So I could see a crazy scenario, where the dealer made a mistake, and the player verbally surrenders and mucks based on that mistake, but the mistake is identified immediately and just as those cards are being drawn into muck, and the cards are still identifiable, so they are allowed to be retrieved.
I think the analysis of the situation in the video is pretty correct, in that the hand of the player who threw his cards in the well, should be considered a fold.

If your hand hits the muck at all it should be over. If you flip em over into the muck and they’re exposed than the hand plays itself. But if they’re down and in the middle hand over!

Once the player threw his cards hand should be over.