I doubt if there could be someone who is born with gambling talent, there is nothing like such, from what I've seen so far, I haven't met a consistent winner, everyone is always struggling with winning no matter how hard they try.
Even if there are lucky days, it does not even last longer, lucky days are always one day, I haven't encountered consecutive two days of winning, always one day of luck.
Imagine this, to be expecting a born winner, nah.
You are right, such kind of incidents are not usually a secret, if someone was born with such gift that they can win as they want, they will be making casinos go bankrupt. You understand? Even if it's just few persons that has such gift, they could use a very huge amount like $100m (or more, depending on the casino's maximum wagering amount) to stake in a game, knowing that they are going to win and by the time they win like that few times, the casino will definitely go bankrupt and they can move on to another casino. Such event will not be hidden but there's nothing like that.