TFT my opponent lost multiple times and their hp didn't go down

I just played a match of TFT and there were three of us left. He had 46 hp and I had 42 and the last guy had like 12. I fought and won 3 or 4 times and his hp never went down from 46. He wins once and my hp went from 42 to 10 in a single round. he then gets a champ up grade and a level up and wipes me out with his Draven with 3 items. There is no way he should have lost 3 or 4 rounds and not taken any dmg, he should have lost if the amount of hp i lost on loosing a single round was any indication.

So in order of likelihood I'm guessing either there is a bug, TFT has a horrible flaw in its design that needs fixing, or most unlikely he was cheating in some way.