Possible Teemo stealth bug

I'm not sure if this is a bug or if it is a result of changes in Teemo's stealth mechanics, but it happened to me in a couple of games. I get "visual cues" of where Teemo is. If he's in the middle of a teamfight these cues aren't noticeable, but if I'm searching for him in a not very large area it's rather easy to detect. I don't have any images to show you what I'm talking about, but what I see is like a glimpse of his outline, a "ghostly" figure of teemo that lasts maybe less than a second. I can't really tell how frequently this happens. In both times this happened (1 in Sums Rift and the other in ARAM) no stealth detection mechanic was being used. Is this supposed to be happening?