They lucked into a straight flush even though their pre-flop cards were unimpressive. That's a bad beat with two capital Bs. Other examples of bad beats include losing four of a kind with Kings to four of a kind Aces or having a full house that loses on the river to a higher ranking full house.
Omaha is considered, by some, to be the hardest game of Poker to master. Of all of the different games of Poker, Omaha is for many the hardest to learn to play and the hardest to bluff in. It is played most often at fixed limits, like Texas Hold'em and pot limit.