What would happen when someone recovers from amnesia?

hi this is for a story; what wold happen if a person who has amnesia remembers his past? for example if a person has amnesia and he forgets who he was and after some 5 years or so he see or does something that sparks something inside him and he remembers his past, what will happen? will he remember the 5 years that he had amnesia or will he forget it? by that i mean will he forget the 5 years and suddenly remember who he was, be the man he used to be.What would happen when someone recovers from amnesia?
Generally people who suffer from amnesia from a traumatic head injury, heal very slowly. They will begin to remember certain people, things and events but it is a very slow process. I have never known anyone with a severe head injury (resulting in amnesia) ever completely recovering all of their memory function,.