[wm r the rake]

i was playing 5/10nl when this hand came up. I was not in this hand however i would like to know what people think of this ruling. 2 players are heads up with the flop coming 4jk all hearts. Player a checks and then player b goes all-in for $600. Player a sits there and doesn't do anything for a while and then his friend sitting right next to him encourages him to call because he knows that player b is on the nut draw. Player a sits there and says your right i call and flips over jk no heart. Player b is outraged and demands that the hand be dead since he was enticed by his friend to call his bet. No heart came and the pot was awarded to player a. The floor was called and they let the hand stand as is. Just wanted to get some feedback, is this ruling correct?