I know exactly what you're talking about, and yeah it is hard to convey. "I once looked over the shoulder of a friend who had spent 1 hour trying to track down a bug and in 2 minutes I lead him to it," isn't exactly fitting.

Personally, I list programming competitions that I have won, and hope that can convey the idea. But lacking that, I'm not sure how I'd try to convey it. "Firm grasp of ubiquitous programming and debugging principles," or something like that, perhaps?