I've played nearly 2000 games of Cribbage on here, I must have had it at least once. The odds are about 1 in 1000 when looking at the maths. Allowing for multiple cribs per game, statistically I'd expect about 4 in my time here.
I suspect the real odds are actually lower because some players won't put two of the same suit in to the opponent's crib.

got a flush in your crib? just wondering ...thanx