[Milhouse]

Q1: is it possible I've managed to delete art files from my media folders, using any of the scripts ?

The only files deleted by the script are cached artwork files in the Texture Cache "Thumbnails" folder - in most cases this will use Kodi JSON TextureDB API to actually delete the Thumbnails files.

None of the scripts (texturecache.py, mklocal.py) will delete files from your media libary. mklocal.py is the only script with direct filesystem access to your library, and it will create (ie. download) new files but will not delete artwork files that already exist in your library.

If artwork files are disappearing from your media library, it's not through the action of these scripts.

Q2: at what point does it make sense to start with a fresh empty database and re-scan the whole thing ? Chasing "some are listed, some are not" is getting tiresome. If that is the better way to go, are there any tricks to know about doing this within OpenELEC ?

If you've lost control of your media library, now would seem like a good time to start again.

However, if artwork is randomly disappearing from your library you need to carefully review what processes you are using to manage your library as I'm pretty sure my scripts will not be responsible for your artwork disappearing, and unless you identify the cause it's likely to continue.