Telephofee:
Sounds like the meds caused a black out. Some have experienced black outs from drinking too much. Like alcohol, medication, when taken in high dosages, can cause an amnesia-like effect.
It's downright scary not knowing what you did, what went on. I know ''cause I've been there. In my early 20s I regularly drank to the point of blacking out.
As for recalling the night's events...Well, it is possible. The memories are stored in your brain somewhere. It's just that you can't seem to access the file. Sometimes, allowing your mind to slowly work on the problem in your subconscious while you go on with everyday activities can bring a lost memory to the surface. In other words, the harder you think, the less you remember. Allow your mind to pull these memories out on it's own. In time, it may come back to you.
On the other hand, sometimes our brains withhold memories from us as a way to protect us from things that we're still to fragile to handle. Maybe the trauma you suffered that night is more than you can deal with right now and your mind knows this. It may be shielding you from pain and heartache.

-Bean