Nunu & willump visible in the FOW upon channeling W

so i was playing a game, and nunu & willump bot were the enemy junglers. and apparently, whenever they used W- Biggest Snowball Ever! i could see them over the Fog of War, even when we have no vision, during his cast. I would provide a vid in the replay, but it shows the snowball automatically, in which i only saw his icon in-game. anybody else realize this potential bug?