I have to agree with you that trauma and pain either gets forgotten by the conscious mind and pushed down the deepest depths of your subconscious as a way for the mind to protect itself or to be such a vivid memory that it stays with you and you remember it just like it was yesterday.
I was barely 2 years old and was having a haircut when my eldest sister was teasing me and I reached out and then I remember the sharp pain and the warmth of the blood that flowed when a piece of my ear was nicked by the barber.
I remember crying but also in shocked.
It seems I am a person who remembers more those painful moments in my life.
I think it is hardwired. when it comes to risk, a loss has twice the impact of a gain so I assume that it is the same with trauma or happy events.