When we sleep or get knocked out, we are aware that we've been unconscious for a period of time. But there could be other cases where we effectively lose consciousness for shorter periods of time - seconds perhaps - and the brain produces illusion of continuity, in the same way we get blind during saccades and the brain masks it out from our awareness by synthesizing data and screwing with the clock.
> When we sleep or get knocked out, we are aware that we've been unconscious for a period of time.
Not always, at least not in the ways that matter.
When I was a teenager, there was one occasion when I went to bed at night, pulled the bedsheets over my head, and with no subjective pause or discernible change of subjective internal experience of my mental state everything became bright, I pulled the bedsheets away from my face, and it was morning.
We’re completely unconscious when sedated or knocked out.