Reminds me of my first experience. The trip involved getting something huge, like a big sense of "oh, I finally get it" but now, 3 years later, I'm still trying to figure out what I actually got.
> “If the doors of perception were cleansed every thing would appear to man as it is, Infinite. For man has closed himself up, till he sees all things thro' narrow chinks of his cavern.”
Also, selective amnesia is a common effect of various drugs, including high-dose LSD trips. Dreams are also easy to forget upon waking, leading some to recommend that you try to make what you do remember from dreams (and from trips) concrete in ordinary waking consciousness, through artifacts such as art, music, etc.
Some psychological theories posit that there is a mechanism of repression that occurs when the mind resists the brining of certain subconscious material to consciousness. This is one reason that some therapists recommend one does not venture too deeply in to the subconscious without a trained guide. You might not be ready to handle what you find on your own.