Perhaps, even if there is no audio recording of it being said or if a ref can't consolidate Mam's claim (You would have to assume a ref wouldn't have heard it, otherwise Leniu should have been sent from the field), maybe the NRL twist things as Leniu bringing the game into disrepute with his post-game comments regarding such a serious allegation?? He still gets a suspension, but at least it isn't a suspension over a he said she said?
I'm just tossing shit out there, but if anything it will be messier if it can't be proven.