The last time something like this happened, was nearly 3 years back, around Feb-March 2005.That one came from a specific IP address in Australia, and I was able to track back the person to his email address, and sent him an email.
How did I know it happen this time? Below's what the log said. Of course, I was able to trace back this to a specific country - Malaysia. So, she uses IE 6.0, Windows XP, and has .NET 1.1 installed.
2008-02-18 15:53:54 GET xxxxxxxxxx/default.aspx - - 60.50.244.7 Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.1;+SV1;+.NET+CLR+1.1.4322) - http://sg.search.yahoo.com/search;_ylt=A0oGkucCqrlHKA4ByFcj4gt.?p=xxxxxxxxxx&fr=slv1-msgr&ei=UTF-8 200 0 0 9120 9765