Moving files (manually in Finder, via terminal MV, or via script) appears to leave a 'ghost' file in search results that cannot be deleted
So, the solution is that the EXTERNAL drives, for whatever reason, were not re-indexing Spotlight.
I ran this command directly pointed to the DRIVE itself, and this cleared the results.
sudo mdutil -i on /Volumes/DRIVE_1
So, the takeaway is: Spotlight re-indexing (sudo mdutil -i on /) is only for the main HDD. Which, is weird, but that's what did it.