So, I got busy when I originally posted this, and as it was more of an aesthetic annoying issue than a performance issue I was able to ignore it for a couple of months. Thank you to those who tried to help back then and to anyone who is willing to take on this challenge today. The stuck document saga continues:
Several weeks ago I noticed the storage space on my internal hard drive was approaching full and most of it was that stupid vague yellow Other category. (Why can't I get more detail about what that actually is?) I don't save anything except my applications and Lightroom database and backups on my internal drive so I was worried. I took it to my local Apple repair shop, their diagnosis was that I need a new internal drive, I said, Yay, that will take care of that pesky stuck item in the trash too.
Nope. When I was back home, at first, before I plugged in my 3 EHDs, the trash was indeed empty, BUT after plugging them all in, it returned. Also, even though the Apple tech removed a bunch of movies from my internal drive that I'd forgotten my daughter made, the Other category was still over 50% of the entire capacity of the drive. So I backed up everything I could think of to my EHDs, then took my Mac back and asked them to just do a clean re-install of El Capitan, no copying back old data.
Again, the trash can was empty at first, but (I should have seen this coming), after I plugged in my three EHDs, that very same XLS document that has been stuck in the trash for 3 months came back again. And I made it worse because one of my "bright" ideas was to try dragging it out of the trash to the desktop so I could delete it. Now I have a copy of it ALSO STUCK on the desktop. When I try to delete the copy on my desktop I get the same error message I've been getting when I've tried to delete it from the trash for the last 3 months: "The operation can't be completed because an unexpected error occurred (error code -50)."
By the way, I have checked permissions in the Get Info dialogue box and the document is set to Read & Write for everyone.
First I tried Apple chat support but when they had me chatting on my phone in preparation for doing things on my Mac that required restarting and the connection was broken I decided to go to bed (it was 3 a.m. after all). But this morning, after some other searching, I remembered this thread, and the link to XLab that Kappy shared was clearer on the terminal solution, which I'd tried several times before to no avail, and my trash can is finally empty!
But only for the moment! It only worked after I unplugged my EHDs. I've got it narrowed down to 2 of the drives being the culprit because I had plugged in one of the drives immediately after bringing home my Mac from its first trip to the repair shop, and the trash remained empty until I plugged in the other two drives the next day. So as I type this, all 3 drives are still unplugged.
So now I'm hoping someone can tell me ...
1. How can I delete the stuck copy of the document from my desktop?
and
2. What to do about plugging my EHDs back in, so I can prevent this item from returning to the trash can? I have to plug them back in eventually, especially the one I routinely use daily (which is one of the suspects, the new one I bought in mid-November, although it's probably the other little one containing some items my husband asked me to back up, because the stuck file is one of his work files; though it could have been backed up on my older EHD that I was using before I bought the new one. Sorry if that is confusing! I can explain better if it would be helpful to understand which EHD is which.)
Thank you! I know this is terribly long, but my computer problems always seem stupidly complicated.