Gnar's disappearing boomerang

So every once in a while, if I Q towards a minion, and Gnar's auto or something else happens to kill the minion just before the boomerang touches, it will disappear and then reappear again on it's way back after hitting another target or getting to max range. Played about 10 gnar games in the past few days and it happened pretty much every game during laning phase.