I believe so..My husband tried it on me.. but I wasn't upset. He seduced me..haha
Yeah it would seep into your dreams and you'd wake up moaning.
That would never happen to me. I sleep alone.
Maybe, maybe not. If he slipped something in your drink, near bed time. You might not notice and sleep too sound to be woken. If you are a hard sleeper, or a sleepwalker, they have been known to have sex in the middle of the night and not remember it the next day.
I knew a man who was often surprised to find out from his wife, that they got frisky in the middle of the night. He never had memory of it. Part of why they had one kid after another, when he was trying to slow down the rate at which they were having them!
There is a condition similar to sleep walking.... So perhaps one would wake up with no memory of it.
If you were drugged or drunk, or an extremely heavy sleeper you could sleep through it. But chances are you would know when you got up the next morning.