Did you GET an IP address? If so, plug it into an WHOIS at ARIN and see who owns it.
http://www.arin.net/whois/
You can maybe do an nslookup on the IP to find out if there is a domain associated with it. For most commercial ISPs, that's a long-shot, but in some cases you might find a modem or access point name, which would likely have geographical information embedded in it.
One way or another, you'll need the authorities involved. But you could at least hone in on the geographical area to point them toward.