Huge vision bug with Nunu & Willump, we could see them whenever they made a snowball!

First things first, here is a video of this bug.

When my friends and I were playing tonight we noticed that whenever Nunu & Willump started rolling a snowball, we could see them for about a second on both the minimap and on the actual rift. This was happening the entire game whenever they made a snowball and my entire team could see it. This is a huge issue because it meant that we could see them at all points of the game and play around them with impunity. Riot needs to fix this for them to be playable.