AFAIK, date-rape drugs are similar to the drugs administered to endoscopy patients.
The drug induces 'compliance' with instructions - even though the normal (undrugged) reaction would be to fight the (unpleasant) activity, then, after the patient has slept, they awake with all memory of the period erased - there is no possibility of recalling events - none at all.
It isn't 'just a dream', there is just a totally blank period (and no sense of 'missing').
I have had several 'endoscopy' procedures under the influence of memory drugs that, apparently leave you alert and aware during the operation but then wipe the memory.
For the first one I emerged from the theatre and gave a full verbal account to my wife of what had happened, then, after a brief sleep awoke and denied of all knowledge of the events.
For subsequent operations I was unaccompanied, but I have absolutely no recall of any intrusive activity.