Don't give them money because you aren't able to keep your email address updated? Don't give them money because you are not able to provide the information they need to verify you are who you say you are?

I've worked costumer support for many years, and me and my supervisors would have rejected your request too. Since you can't provide what they want (not even a definite nickname wtf), you probably can't prove the purchase either.

Don't flame some poor support guy, kick yourself in the ass for letting it slide for so long that you cant even remember the original nickname anymore and chalk it up as a learning experience - we've all been there.