In OS X you can drag+CMD to move a file between devices (rather than copy). Basically this involves the transfer of the file to the new destination and delete it in the old location. However, I have noticed in Yosemite that in some cases the "move" does not actually remove the file in the old location, and this with no warning. Further to various tests, it is possible to replicate this simply. Open a PDF file in preview and then move the file to a new server location. Since the file is open it will not be deleted in the old location. This without warning. I can understand why the file is not deleted in the original location, however I cannot understand the absence of a warning.