Clown Breaking Bottles on his head
Not exactly sure what the collision is, or how to replicate it. But it happens a lot. I'll be chasing, wind up to throw a bottle in front of my prey, and the smoke just spreads around me like I hit myself. It happens on indoor and outdoor maps (swamp and meat plant ie) And I've stopped and looked for overhangs on a few occasions and found none.
It can happen at all power levels of the throw, but might by tied to angle of the throw.