While Lee is correct there can be some problems in this situation that could cause the player mucking the hand like that to lose the pot.
The first problem is that video is not available, or the video is *so bad one cannot really figure out what the hand is. It could also be policy at a casino that they do not stop the game and run video, they feel it is the players responsibility to protect his hand, and if he misreads his hand and mucks it before the other players have a chance to read it, the player may have no recourse.
Most of the time in this kind of situation, players have looked at the hand, and the dealer has looked at the hand. If a floor person is called over they will typically rule that the hand was what was seen if they can verify it with a couple of players.
So the answer to the question is what lee wrote, they hand is live the pot is awarded even if the player mucked the hand after it was turned up and shown. Just be aware that things have and will go wrong on occasion. The lesson being pay attention and protect your hand until the pot is awarded.
*Modern casinos typically have pretty good video equipment. However it is still pretty tough to tell what a hand is at times. The problem is that the camera may be twenty or thirty feet away up on a high ceiling and may also be shooting at an angle. The environment is pretty dynamic with people moving around, blocking shots and messing up the auto focus. Also there is no guarantee that every table will have a camera on it. You may notice in some card rooms with big Jackpots that they have a camera above every table to record jackpot hands. Even these might have problems because they are focused on the center of the table and things like an upturned hand in front of a player may not get recorded as well as one might hope.