Friend was blackout drunk and eight hours later seems all sober, what is going on here?

So a friend of mine had few drinks yesterday and at some points he goes from sloshed to stumbling to barely conscious within 20 minutes. I brought him home, carried and dragged him to bed and he slept a few hours. Just had a phone call with him and he doesn’t remember anything from the way home but feels and sounds totally sobered up. He didn’t seem to have that many drinks and I don’t think his drink was spiked. But if I was as wasted last night I would not be in any condition to even have a conversation at this point. It might not be crucial but he‘s of Eastern Asian descent.

Is this a common thing? I‘m equally baffled and worried about it.