This is the command I used!
sudo mv '/home/alex/Desktop/elementaryos-0.4-stable-amd64.20160921.iso' Computer
I can't find it anymore, I wanted it to put it on Computer to make sure that UnetBootin can see it, but didn't succeed..
That command renamed my file Computer, and moved it to a folder that I was able to find it with search option. After that I renamed back to ele....iso and moved it to the desktop!
Computer
is a subdirectory of the directory you were in, you will find the file in that directory. Most likely however, there isn't such a directory, and you just renamed the file toComputer
...mv Computer elementary.iso