Questions about example sentences with, and the definition and usage of "Missing"

A: missing children = children that can not be found
missed children = children that other people feel sad about not seeing / children that were not hit by something (?)

A: The location of the children is unknown. They're missing and that is obviously a cause for a lot worry.

A: “You’re missing out” means that something is cool or fun, but you haven’t done it, so you haven’t experienced that cool/fun thing.

For example:
“Did you see the new Avengers Infinity War movie?”
“No”
“You’re missing out. It was a good movie.”

A: There like exactly the same