Pink Ward Bug [Game Play]

My friends and I were playing a game and the enemy support had put down a pink ward in the on tops side spot of the photos and it kept disappearing on us until we realized that if we go behind the wall or the minions aren't there going towards the lane it becomes invisible and still provides vision. We got into a custom game and tried it out and it still worked. We also did it on purple side and it still happened. It may not be a huge bug, but its there and could be broken if nobody catches it.