I haven't seen the incident on the television but it seems Misi kicked the ball away from the attacking player.
I have read The glossary in the rules and the interpretation for a 'foul' is as follows -
1. A player is guilty of misconduct if he:
(a) Trips, kicks or strikes another player.
(b) When effecting or attempting to effect a tackle
makes contact with the head or neck of an opponent
intentionally, recklessly or carelessly.
(c) Drops knees first on to an opponent who is on the
ground.
(d) Uses any dangerous throw when effecting a tackle. ( From Section 15)
Therefore the 'foul' play,for a penalty try,has to be made on the player.