A long time ago I read somewhere that most mishaps happen in the last leg of a journey, when folks start to relax their guard and anticipate the end, and I realized that's happened to me several times. The times I've gotten lost, it's most often been on the last leg, when I thought the decision making part of the trip was essentially over, and I made some stupid mistake, or missed something I should have seen. I've been able to compensate for the phenomenon a bit just by being conscious of it, and I no longer "let my guard down" until I'm ALL the way back.

It sounds like the same sort of thing happened here- where your familiarity with the area actually worked against you, by making you just a bit too relaxed about it.

As for map and compass, I learned that lesson in a slightly different way. Without going into a long story, unless you've experienced it, you just wouldn't believe how strange and unfamiliar even the most well-known trails can become in a heavy fog. The whole world changes, you can't see anything more than a few feet away, and nothing looks "right" anymore.