When my wife had a colonoscopy, the sedative they gave her caused her to not remember anything for almost an hour. She not only doesn't remember anything from the procedure (and that seems a good thing considering what was going on), she didn't remember talking to the doctor afterwards.

A couple years later, I had a test where they ran a scope down my throat. I clearly remember everything up to the moment when they gave me the sedative. I don't remember the gurney ride back to my room, the conversations I had, or walking out to my wife's car for the trip home. It continued for another 20 minutes or so after I got home. Later that day, I read the paper with a strange sense of deja vu. I'm pretty sure I read it after getting home but was still under the influence of the sedative.

This must be what happens with the "Date Rape" drugs like roofies. The victim is sedated and can't remember anything about the rape. Scary.