While it's possible to argue that a novice poker player may make a mistake at the table, that argument doesn't hold up if it involves an experienced poker pro. That was the excuse Brazilian poker player Rafael Caiaffa made during a recent tournament, but his antics have cost him an indefinite ban from the game.
The royal flush is a case of the straight flush. It can be formed 4 ways (one for each suit), giving it a probability of 0.000154% and odds of 649,739 : 1.