[Gameplay] Teemo's poison

Okay so I've only noticed this in one game so I'm not sure if it was just that game, but I figure it's good to post something to see if others have had this problem. The other day was playing a bot match as with support (don't judge it was a bot match) and when would kill via poison would come back to lane with the poison thing over his head but not do damage, and anytime would walk under turret range it would attack him even though he hadn't attacked since he respawned. I'm not entirely sure but it seemed the poison thing would go away only after I attacked . It didn't ever happen to the that was top lane either. Anyone else notice something like this happening?