My old ex-classmate appeared in a dream after I saw him for about 2 seconds

[Nfri]

So yeah like a title says, I was driving car when I saw my classmate (not close friend, just classmate) from primary [~10 years ago] school drove against me. I noticed him for two seconds passing my car on the road. Then I though about him for like 2 minutes. This short event caused his manifestation into my dream that night. If I knew, it would be a effective dream sign. Also when I compared it to hours of reality checking, dream signs visualization or dream incubation, it would be very neat to understand what causes his appearance and the concept of dream creating. My idea is that I've spend a lot of time in class with those classmates and my subconscious is still filled with these memories. Seeing him was a trigger to my young subconscious part.