K3 is a "named" hand over that some of the guys at Negranu's site like to bluff with. Every time you get the Krablar in an unraised pot, you raise preflop and bluff like it's the nuts.
I should go check for a 'bad beat with a Krablar hand' post to see if it was one of them...
Of course, if it was, he misplayed it. You're supposed to push in on the river if you're just getting called down.