That is a sad thing that a child that age would experience that. A child that age doesn't understand something like that, an adult would have a hard time experiencing that. It is also actually normal to feel detached while you are thinking about this scenario in the now too. Children are pretty resiliant because they don't understand a lot of things "yet". Most children are more apt to ask questions about what something means and "why". A six year old is really at the point developmentally when their brain has just formed a one personality too and they really don't have enough there to understand what to do with an experience like that either.

I noticed this is something that Disney had happen with his main charectors too. Bambi, Cinderella, Dumbo was separated from his mother, Mogli in the Jungle Book to name a couple off the top of my head. Yet, other Authors had their charectors have a similar challenge like the famous series "The Box Car Children" and "Huckleberry Finn".

You are at a point in your life where you have the ability to think about this more and what a loss like that has meant to you in your life up to now. There is a mourning process with that too, about what was "lost" to you in that challenge. You are now 21?
Well, that is at a point when an individual is trying to figure out who they are and what they want to do in life. Often one feels presured to know the answers, however, the average individual this age really doesn't quite know yet. It's ok to be at a place where you are taking an accounting of your own history up to this point too. It's just where you on your level of maturity are right now that is actually "normal".