I don't know that you can get back what you have lost. Check to see if you have auto save on...on my version it's under Tools, Options and there is a tab marked Saved. I have mine set to autosave every 2 minutes. It will show you where the autosave goes but I think you can only recover that if you haven't shut down. (I could be wrong). Try nanaquilter's suggestion
I try to get into the habit of hitting the save icon from time to time so I don't lose everything