Man, there's some bad info here.
You probably ate a psilocybe species, which is strictly a hallucinogen, NOT and opiate or especially not a delieriant (something that makes you insane). The reason it seems so natural is because it is only a single OH molecule away from being human serotonin.
There are a few species that actually contain serotonin.
You could have eat an amanita, which could be considered a delierient (sp?). If you had a hallucination that seemed like it was really there, like really really there, you might have eaten an amanita. unlikely tho.