This gave me a good chuckle, but as the first comment in the thread states, this would be pretty hard to do without the admin password. If this is real, then I'd say all the blame is on the owner of the computer for having it in a state that allowed his /bin to be so easily deleted.
If you have a running shell, you will have at least the shell builtins, which include things that will let you list files (echo *) and write out data; you could, in theory, use echo or printf to generate a simple netcat binary, and then use that to restore /bin.
Probably easier to just boot from a USB stick and restore though.
[edit] And of course many systems have useful binaries in /usr/bin due to old hard drives being small.
Nothing that can't be recovered from though.