Kayle's Ult wasted on After-Death KogMaw

I just played an ARAM, where I played as Kayle and we had a KogMaw in our team. Near the end of the game, I wanted to use an Ult (the shield) on him, but it was too late. However, instead of nothing happening, the purple KogMaw essence (whatever it's called) that can move after KogMaw dies has recieved the Ultimate from me, and thus it was completely wasted! It practically lost us the game, because we couldn't protect the base after that, while we still could have won. I'm surprised a bug like that hasn't been fixed yet and it irritates me greatly, neither Kayle or Kog are new champions, so I would really like to know why the heck is this possible. I know that the idea of placing Zilean's bomb on KogMaw is pretty enticing, but why is this Kayle's buff (and probably a few more completely pointless buffs for this instance) working?