A Library folder structure looks like:
Library_name/Author_name/title_name(ID#)/formats,metadata.opf,cover.jpg
If you don't see a title(###) folder, things is really busted
Open a metadata.opf with Notepad, that ws the backup of your metadata for that title. If that is trashed, empty
(btw that would also say USER action, not the update), which would make the recover operation fail. You need to import the books into a NEW-
EMPTY library