Invisible ability on Arclight Velkoz?

Unfortunately I don't know what the ability was. I just know I was relatively close to a turret mid-game in ARAM and suddenly he killed me, with no visual indicator of what happened. I was baffled and typed some sequence of question marks in chat and was an idiot not to check the ability name in the recap, only the damage. Not that it would've helped, I don't play him. From what I noticed in the patch notes, usually over 50% of the Fixed bugs section is about skins, so I just wanna know if it's a known issue, or I just blinked for longer than normal. Any noticeable lag usually shows the reconnect bar for over 10 seconds, not one, so it wasn't that.