[takoi]

This is how I imagine it working:
- the addon would be a service that runs sporadically (perhaps on a library update?)
- it creates a folder structure in the addondata folder for every tv show
- it scrapes the tv show info (season, episode #s) from the usual sources (this folder would need to be added to the XBMC sources file)
- it detects which shows are missing (perhaps the user has the option to only do this for episodes that are after the first non-missing one)
- for each show that is missing it adds a copy of a very very small video to the dummy folder structure with the episodes details
- the video just says "episode is missing" if you run it
- it could then change the display name of the episode in the video database to include *MISSING* to the start, this means that it would be obvious on all skins that use the display name
- each time it is run, it checks to see if any of the missing episodes have been found, and it deletes the database entry for the dummy file if that is the case.

And that is why this can't or shouldn't be an addon. Kudos for creativity!, but the solutions is at best a hack that require lots of user setup and will only work in some situations. There's too many core parts involved here (scraping the informations, storing it, to displaying it in the library) that add-ons don't have access to.