[danso]

This is a Hail Mary, but I've found some important email address by running a WHOIS on that person's known web properties. While he may have hidden his registration info for his personal site, he may have slipped up on his project sites

[msumpter]

You can also use tools like DomainTools.com to look at historical registration data, their data may be private now but could have been exposed previously.

[ktf]

I've had great luck with this, actually. At the very least there's a chance you'll find some dummy address that forwards to a real address, and get a response that way.