Doing a Whois should at least get you some contact names and numbers: http://www.networksolutions.com/whois/index.jsp
Second, put in an order to transfer the domain name with a reputable registrar like: http://www.enomcentral.com/
While that may not get the domain transfered, they may come up with more contact info.
The lesson from this should be that the domain name is much more valuable than the site files. They can usually be easily replaced... keeping that domain name safe... that's really what counts.
If the old registrar allowed transfer, resold the name within 12 months of expiry (known as rehab or dormant) then your friend as the previous registrant may have legal ways of reclaiming their property...