Well... I need more information then that.
How long you guys have been together, do you still talk or see each other everyday? Stuff like that.
If you guys do see each other then it depends how attached they were to you and how much game you put up.
If you guys lost contact, try to find them again. I don't think they will come back unless they are really hung up on you. But you should put some effort into it, and ask them if they still like you if you still have contact with them. Or try to talk and build stuff up again.
Once a wall was built, then destroyed its easy to build it up in the same place and same way.

like the saying says, if you love someone let them go, if they come back they are meant to be yours, if not they never were! Good luck =]

Maybe if it was truly meant to be