No, seriously, why? I hope it's because there was a topic you're interested in. You didn't say, but it'd have to be an awfully bullshit topic to have no interest to anyone anywhere.
Obviously sending in resumes through the front door is a waste of time. Work your network.
If you just did a PhD to kill time, then you're just a C++ developer who's been out of work for six years. If your thesis had nothing to do with the job you're applying for then *FOR THEM* you're just a C++ developer who's been out of work for six years. Maybe they wanted to know if you're aware of C++11 or whatever and that's why they were asking those questions.
But, for Pete's sake, you owe it to yourself to discover who your network knows (do you do LinkedIn?) in an industry that could use your interest's knowledge, and apply it. Unless you decided that after the PhD you hate that topic (it happens) and then you're just starting over.
You should have made friends with all of the faculty at your school while you were there, and not hidden in a cave for six years. Did you do that? Ask them for favors - maybe you can return them some day. The way it works is they help you then you help then, and it's a non-zero-sum game, but somebody has to go first.