Oh my god this is almost EXACTLY what happened to me in my only ever bad trip on magic mushrooms. Fortunately I was at home, so I lay on the floor for what felt like forever but was probably only an hour or so, and experienced a barrage of memories completely out of order, but all incredibly vivid.
And the thought loop I was stuck in was "how can I understand subjectivity from inside subjectivity" (the hard problem of consciousness). Because it's a paradox, it felt like every time I ran into the impossibility of it my brain glitched and tried to rerun the program, so I had that thought probably thousands of times.
At the same time I was having such vivid memories - from the most random times in my life, including childhood, but not just memories of real events, but memories of dreams, and memories of the mental imagery I get when I'm reading books, and they were all equally vivid and "real", and I couldn't distinguish which were the real memories and which were the dreams and books, and besides they were out of order. I began to panic that I would never be able to function normally again because I wasn't able to construct a linear narrative of my life. I clung to the knowledge that it would pass, that it wouldn't last forever, even though that felt like faith and not based in any actual certainty.
I have never taken mushrooms again and I never will.
Part of the reason why is because a few weeks later my fiance also had a bad trip on mushrooms, but far FAR worse than mine. He entered a completely delusional state where he believed a dear friend who was tripping with him at the time, was a murderer who had poisoned him and was trying to kill him. He shot her and is now in prison for manslaughter. For over a year afterwards the delusions and dissociations persisted, and sure I know he had mental illness before this trip, but it REALLY exacerbated it to the point in the worst cases it was like schizophrenia. And it didn't just go away once the drug left his system either. It has taken years to recover.
I think the dark side of psilocybin is something the public NEEDS to know about. Not scaremongering propaganda, but real education from people who have taken psychedelics and still feel positively about psychedelics overall. Psychedelics are medicine. They are not a drug you should take for fun, or frivolously. They are not something you should take if you are mentally ill, unless you're with a seasoned trip sitter and/or therapist!
I think the unpredictability of mushroom dosage is one of the reasons they're more likely to cause these kind of bad trips than say LSD. I have never had a bad trip on LSD, granted I have not taken a "heroic" dose for over 5 years. But with LSD I know how much I'm taking. With mushrooms, both me and my fiance thought we were taking a "low dose" because the physical amount of mushrooms was similar to a low dose we'd had in the past. But every mushroom is different. And because there are many kinds of psilocybin mushrooms who knows if other chemicals may be present that can interact with the psychedelic compounds.
I am by no means anti-psychedelic. Even with everything I and my fiance have gone through, the pain and harm that risky psychedelic use has caused to us and most of all to our deceased friend - I believe the positive effects of psychedelics in general outweigh the negatives. I do not regret taking them, although I regret my fiance taking the mushrooms on that specific day he had his bad trip.
Part of it was because we did not know about the extreme end of the bad trip spectrum and how dangerous it actually was. We didn't know for example about the case of Thomas Chan, a Canadian man who had an almost identical experience on mushrooms as my fiance did - and who stabbed his father and mother while believing they were demons. It's rare, but it can happen. Psychonauts need to know this! Yes the government tried to malign psychedelics and make out they were the worst thing ever and that was wrong. But that doesn't mean they're harmless and while extreme harm is very rare, it's possible and you need to be careful and design your set and setting with the possibility of a bad trip in mind.
And I agree with you, the claim by some psychonauts that "there is no such thing as a bad trip just a challenging trip" is naive and not based in reality. Anyone who has had an ACTUAL bad trip will not say this.
And your trip sitter should CALL AN AMBULANCE if the trip goes as badly as it did for my fiance. I don't care if psychedelics are illegal where you are, it could save a life!