2013-08-01, 23:48
Why would System(a) have deleted the artwork files?
Obviously that's your problem though - you scanned in the library on System(a) which meant the artwork has been cached locally, the artwork was then subsequently deleted by some process (maybe XBMC, maybe not) but because the artwork had already been cached on System(a) it's still visible on System(a). As the artwork has now been deleted, there is nothing for System(b) to cache and display. You need to restore the artwork.
Obviously that's your problem though - you scanned in the library on System(a) which meant the artwork has been cached locally, the artwork was then subsequently deleted by some process (maybe XBMC, maybe not) but because the artwork had already been cached on System(a) it's still visible on System(a). As the artwork has now been deleted, there is nothing for System(b) to cache and display. You need to restore the artwork.