Kennen Bug

I was in a game with a friend of mine and we encountered a kennen (not so special). When he reaches level 6 he had his ult and he used it but i didnt saw it, it was invisible. i dont know it has something to do with the champions in the game, Me and my friend didnt saw the ult and the teammates didnt see it either. I hope this is a bug because it was pretty frustrating :(