What you need to do at this point is run pattern a finder directly on
his hard drive to look for private keys directly at the disk sector level.
Yes. This is what the "--recover" option of jackjack's version of pywallet does. It scans the disk at the sector level, looking for keys.
But the owner of the wallet runs Windows, which I haven't used since 1998. I have no idea how to install python on it, or even how to name the raw drive (as opposed to the formatted volume). Nor do I have physical access to the machine, or I'd just boot up a Linux rescue disk and scan from there.
If anyone does know how to do this on Windows, and is willing to patiently talk the guy through it by skype, I'll pay for their time in BTC whether successful or not.
Or maybe there's a simpler tool with fewer dependencies that will just scan the disk for a magic bitcoin pattern such as "30 82 01 13 02 01 01 04 20" (as posted by dayfall). If that's not present, I guess all hope of recovery is gone.