[Gameplay] Zac Immortality Bug

This absolutely bizarre bug occurred pretty deep into a ranked solo/duo game. I dived the enemy Jhin while he was ulting, got hit by Malzahar's ult, and died. But instead of going into my passive, I started running away as the smallest Zac size possible with no health. I went into my passive 5 seconds later, but I was still able to move around in my passive. What's more bizarre, is I instantly became full health as soon as my passive blobs died, only to suddenly be stricken with 3000 or so instant damage.

I have never heard, seen, or encountered this bug before, and I have been playing Zac like crazy for the past week.