I've lost my account how do I retreive it without starting a new castle/game?

If you have previously bound your game then you will need to start up a new game and play through until you have the option to access the settings menu and then you can log into the old game.

If you haven't bound the old game then you can do the came and use the retrieve account option to contact the game support with your details and ask for help getting the old account back.

You can also try contacting support directly outside the game to ask for help.