Girl goes missing, boy never forgets her and continuously looks for her (either a policeman or security work)

[Charlotte]

I'm trying to find a book, loner girl suddenly goes missing after making a connection with a boy at school. The train goes cold and years go by but he never forgets her. He becomes a detective or police officer to help find what happened to her.
From my memory i think she has an unusual name but cant be sure.
Thanks so much

[Kris]

Charlotte, I moved your request to the "Unsolved" folder because it sounds like you're looking for one specific book.

Around what year did you read this book? This will help narrow down the search.

Please read our guidelines for posting a book request - https://www.goodreads.com/topic/show/...

[Charlotte]

Apologies, it's the first time I've posted. I think this was be around 2013/14, starts out as a YA romance and moves on to a few years later.