The auto mount/ idle soft unmount solution issue is a good way to deal with removable media and has been for decades in other operating systems. I expect OS X 10.10 is doing the same thing. It appears that there is some sort of loop back file system pointing to the real device. The problems in Mac land is that $ cd /Volumes/UNTITLED; ls -l will often return ". not found" at random times. Oddly enough I've never seen things disappear from the gui systems.