Polite way: reply to that GM and tell him that your bug report was for D3, not WoW.
Impolite way: post it on D3 forum so everyone can see it and laugh.
Extreme way: wowbash.com it, post it on the D3 forum, make another ticket and say that D3 support suxx :P as they cannot distinguish D3 bug report from WoW one.
But I see this as unbelievable. Either simple mistake (but very compromising) or highly incompetent GM. Please, let it be 1st option...