npm ls -g empty after installing package globally

Question

I normally develop on *nix, so I'm a little out of my element, but trying to assist a fellow Windows developer with npm. Using Git Bash (MSYSGIT), we installed the latest version of npm with:

$ npm install -g npm

Before this, the package directory was empty. But now we can see the package in the directory:

$ ls /c/Users/steve.jobs/AppData/Roaming/npm
npm

However, npm for some reason doesn't detect the package:

$ npm ls -g --depth=0
C:\Users\steve.jobs\AppData\Roaming\npm
`-- (empty)

What gives?