Joplin always stores notes in the sqlite database file, regardless of whether you use synchronisation or not. If you don't see any notes, then this likely means that they aren't present in the database either. Judging by what you've written above, it's likely that you will need to undelete your notes using the method from https://discourse.joplinapp.org/t/restoring-deleted-notes. However, this will only work if you had note history enabled and not enough time has passed to remove them from the database permanently.