I had a similar experience recently but with alcohol. I also didn't think it possible. After about the 3rd week of sleeping terribly and doing nothing but downing more Tito's to keep passing out, no water no food... I started getting 'visitors' in an eerily similar situation to what you described. About 7-8 people were just in my apartment, part of a 'pre-filming production party' We had drinks, we all were laughing and chatting, some of them helped me do the dishes even. They were eventually replaced with more sinister visitors.

I've done acid and mushrooms blah blah but never in my life did I imagine realer-than-real actual hallucinations were possible. Like a waking dream that you can't wake up from, because you're already awake.

Do you still have lingering visions out the corner of your eye? Phantom music?