Please show us a screen shot of what you are seeing. Where do you see this All Synced Files, in what section of the left hand panel?
Have you used the File Manager for your OS to verify the images are no longer in the folder you placed them in originally?
LR doesn't move files around on your hard drive by itself. Doesn't happen.
Top left in Library mode, just under all photos. Not on that computer now; will send you a screenshot when I am on it.
When I moved photos within LIghtroom, it refused to move a few, saying those files were already in the folder. But I did check folders beforehand (in LR to see if images were where I had originally put them, they were not). I didn't think LR would move files by itself, but something went haywire--and I don't think it was user error.
If All Synced Photographs is in the Top section named Catalog that is just a Link to all the images that are synced. Just like All Photographs is a link that shows all images that are in the catalog no matter where they are actually stored.
I just looked my install of LR and I have that same listing.
That Link, "All Synced Photographs", will show all synced files even if they are in different collections, stored in different folders and in different collections.
LR hasn't move any of your files.