I never thought about it as something that can have such fancy name and such broad engineering application. I think my technique is like 1% of what Wikipedia describes.

The old "So you want to be a success at selling?" training video starring John Cleese has a wonderful example of (roughly) the Five Whys applied to sales.

(It can be seen at http://www.videoarts.com/sales-and-negotiation/so-you-want-t... at 15:15 , but alas only after registration now.)

Ishikawa diagrams and the 5 whys are quality control tools, specifically root cause analysis tools.

What OP mentions is taking notes of his though process as he goes along, so he can jump back in after an interruption.

This is the kind of revelation that brings me back to hacker news!

Wasn't the latter inspired by kids? https://www.youtube.com/watch?v=BJlV49RDlLE