Kha'Zix Possible Bug (No, Not THAT Kind)-- Pre 6 Invisibility

I was playing Nocturne in a ranked game, jungling against a Kha'Zix. As I was quite low health, I decided to try and take the scuttle crab in top jungle to regain some health. As I approached, I noticed that the scuttle was being attacked but couldn't see from who. Assuming the culprit was in the bush I backed off towards my own jungle. Then, out of literally nowhere, a bug killed me. It looked like Kha had jumped on me, but I hadn't seen him approach. Instead, he had materialized on top of me. If he had been 6, I would have assumed he had ulted-- but he was also level 3. To say the least, this was not the ideal way to start a ranked game.

I'm not sure if he was somehow hacking or if this is some kind of bug, but I thought I'd report it. I have a video of the incident, but am not sure how to attach it on this forum.