Well, it was so long ago now and I knew nothing about mushrooms then so I can't say with certainty that it was Psilocybe cubensis specifically, but yes, it was definitely psilocybin mushrooms. I have taken Amanita muscaria myself as well and can verify that the experience is quite different, though compared to many things it is still very "psychedelic-like", but ultimately a different kind of trip.
About the dehydration, I'm not sure if that was actually happening or if that guy just thought it was, haha. I'm sure the confusion of the club contributed though. I've actually had psychedelic blackouts since then from nothing more than tripping too hard too, but I do recall specific events that would support the environment playing a role. For instance, the very first blackout came within seconds of going inside; I was stumbling around barefoot and accidentally turned the lights on causing everyone to look up and laugh at my trippy clumsiness, and one guy came up to me and started giving me a light show. I remember seeing the bright lights initially rushing towards my face... and suddenly I was coming to somewhere else.
And yeah, that guy and his baseball delusion was pretty great lol. I don't know how anyone convinces themselves that an extended salvia trip in the middle of a rave sounds like a good, fun time, but he sure made the most of it!