I remember particular events. Like my last ride seeing 40+ pre-school/elementary aged kids riding on the bike trail. Or the goats eating weeds.
heh, I won't forget when me and my friend were at northstar on dh trails and both of us had an intimate meeting with the top tubes of our bikes after riding through a soft berm of sand/moondust and off of it.
Or that time I heard +saw baby bears on a mountain in utah and rode damn fast down that trail and out of there.
My brain seems to be good at "cleaning" unnecessary information, which I guess mundane rides are included in that.