Missing database entries

I was having problems with Calibre (6.2.1 on Mac OS) not finding the library, so I ran a restore database.

Now I have 8 extra titles in the library not in the database which I added to Calibre in March/April and logged them against my LibraryThing account. The titles are all very large PDF graphic novels so once added to the library I remove all formats and just have the metadata and covers but the author/title folders remain in the library.

Is there any way to take the metadata from the folders and restore the database entries without re-adding and updating my LT records?