[GAMEPLAY] Last Turret shot does not hurt!!

I noticed this a few times that the last shot of a tower does not do damage when it is destroyed before the shot hits the target. Yesterday it happened that Vayne attacked our Turret and she was tanking it and she was very low and I saw the last shot of the turret flying towards her but before it could reach her Vayne destroyed the turret. So this shot reached her after the destruction and did no damage and I was like "Yeeeaaah I still get the kill because this MUST kill her!!" ... but it didn't.