That sucks...But this is one of the reasons I like Black Ops sadly. People that dare use sniper rifles ESPECIALLY in close quarters like that are asking for someone to kill them. This isn't MW2. It's sucks you didn't get the kill, but usually things like that happen when you try and be cute. You could have knifed him in the back, stuck a semtex on him or shot ballistic knife if you wanted to be cute. You tried to snipe a guy 3 feet from you.
Treyarch hates Snipers, and whenever I see a sniper, I pick him off WITH MY ASSAULT RIFLE, laugh to myself and think, "just like the mohawk people, just won't let sniping die"