A couple stories where such has occurred: We can Remember it for You Wholesale by P.K. Dick, the story the Scwarzenegger movie Total Recall was loosely based on. The Minority Report the story by P.K. Dick, and the Tom Cruise movie based on it. I'd have to go back and look, but I seem to recall that there are some more stories by P.K. Dick that involve some kind of amnesia or people messing with memory and such.
Also, there were some Doctor Who episodes where the Doctor had amnesia of one form or another. In one, he has removed his memory and placed it in a device so that he can hide from aliens who can read minds. In another, he is in a time loop where he dies at the end, over and over, for billions of years, until he finds an escape. In a few episodes, he meets a time-copy of one of his earlier or later selves that does not have the same memories he does. It's a big wibbly-wobbly time-ee-wime-ee thing.
The movie 50 First Dates is about a person who has no long term memory. Her long term memory stops at a particular day. She lives through each day when she wakes up, thinking it is the next day from the end of her memory. Then when she goes to sleep, she permanently forgets the most recent day. It's very poignant.
Time-travel negative amnesia (where you remember stuff that has not happened) is a big plot point of All You Need is Kill by Hiroshi Sakura, the story that the Tom Cruise movie Edge of Tomorrow is based on.
Stories about memory and amnesia frequently sneak in some questions about what personality consists of, what it means to be you. If you did a lot of stuff that you now can't remember, are those actions part of you? Should you try to get the memory back?
The thing to keep in mind when you write a character with amnesia is, they really can't remember. It's not that they are pretending. The memory isn't there. So, in effect, they are a different person to the person with the memory.
So if they have forgotten events that shaped their personality, they will be different by that much without the memory. If they have forgotten important people, for example, they won't have the emotions that go with that person.
Don't have them doing things that depend on the memory. Have them move forward in their story with the memory they have. Have them do stuff based on the memory.
Until and unless they start getting clues, or partial recall, that is, or maybe the people around them are telling them stuff they have forgotten. You can get into a huge amount of drama between the people who want them to remember and the amnesiac who just wants to lead their own life.
Another thing to keep in mind is, amnesia is a trope. It can become cliché very fast. It's sufficiently frequent in soap operas, for example, that it became a frequent New York Times crossword clue and answer. It did that often enough that it was considered a cliché in the NYT crossword.
The hope is to do something fresh and interesting. That's kind of a big challenge.