Vayne condemns Red through the terrain.

Played Vayne last night and this happened 2 times when I was doing Red buff. I condemned the big one and it dissapeared in that wall that surrounds their camp. Red buff was simply walking back while I was still able to AA him even if it was still inside the terrain. I didnt saw If I actually condemned it in the wall or through the wall to the bush behind it tho but it isn't as it is meant to be.