Cho'Gath Feral Scream not counting and Wu'Kong getting executed by tower after I hit him with 'W'

1. Played a ranked promotion match with Cho Top lane vs Wu.
2. I got caught at level one and was forced to flash back to my tower.
3. I cast Feral Scream as he dashes onto me on the tower and kills me.
4. He is executed and I don't get the kill credit (kill/gold/exp) even though he was hit with the move and took damage and was silenced.
5. Happened again where he killed me under tower with dash and I hit him with Feral Scream and he was executed instead of crediting me the kill.

This issue completely lost me the lane. If I got the return kills on his dives, I would have had the gold income to at least keep up with Wu a little better. Even the other player after the game said that he also noticed that he had the silenced animation above his head (indicating that I did indeed hit him with the spell) and thought it was weird that he was executed...

Edit: Looking back I didn't make this completely clear, but when wukong cast his dash on me, the dash itself was one shotting me. He didn't dash and do some other stuff to kill me. It was just dash. So I died pretty quickly but the animation for Feral Scream still went off as stated before and the silence mark was on his head.