by grizzler on Wed Jan 23, 2013 2:55 pm
They don't actually go anywhere. The filing system action isn't started until you 'paste'. Then they're copied over and after that if the starting action wasn't a 'copy' but a 'cut', the original is deleted (a 'cut / paste' on the same volume is different, but that's not relevant here). If the copy action fails and the filing system notices this, the delete action is skipped.
You write 'It failed'. How exactly? Did you get an error or did it fail silently, i.e. did you only notice the files weren't on the external drive (much) later? In that case I would think you have indeed forgotten to unmount. The files will still be on the external drive, but the mapping hasn't been updated, so they are inaccessible. Maybe file recovery software can help you get them back.