If you can get in touch with this guy that would get you close. how about emailing this userid at yahoo[.com,.co.in], hotmail, aol etc and see if you hit jackpot ?
Or you could reply to one of his friends and just if you can in touch with this other guy via another channel ?
All this is assuming that the other guy cannot get into this "common" gmail account and you are not enjoying looking at all the other emails that you get.
All this is assuming that the other guy cannot get into this "common" gmail account and you are not enjoying looking at all the other emails that you get.