Dr Mundo has invisible clevers

I just got done playing a match of summoners rift while in ranked and i believe i might have found a bug. The enemy team had a Dr. Mundo and my team was complaining about him having invisible cleavers and i didn't believe them. Until i started to gank around 10:00 min or so and i was being slowed by something. Mundo was the only person around who had a slow and i could hear the cleaver hit me but i could not see it. It was like this the match and i thought i would bring it to your attention.

it just might be possble gitch that it happened