Hi there Shwee,
Because this person didn't log in, I have no real recourse at this point. I am, however, looking at extended logging software so I can get more than the last 2000 visits information, logged in or not. With my having seen this now, rather than when you posted, that limitation on logging makes it so TIMEWISE I can't go very far back and actually SEE where this person is coming in from and potentially trace them.
Sorry I couldn't help more at this point.