There's another story I heard once from Rob Pike about debugging. (And this was many years ago - I hope I get the details right).

He said that him and Brian K would pair while debugging. As Rob Pike told it, he would often drive the computer, putting in print statements, rerunning the program and so on. Brian Kernighan would stand behind him and quietly just think about the bug and the output the program was generating. Apparently Brian K would often just - after being silent for awhile - say "oh, I think the bug is in this function, on this line" and sure enough, there it was. Apparently it happened so often enough that he thought Brian might have figured out more bugs than Rob did, even without his hands touching the keyboard.

Personally I love a good debugger. But I still think about that from time to time. There's a good chance I should step away from the computer more often and just contemplate it.