I've had similar experiences while out for a bimble, knowing which way home is without easily being able to say why. I think it comes down to what many people on this thread are saying - having an awareness of ones surroundings, subconsciously picking up on things like the position of the sun, landmarks, etc. That said, while in Thailand I did some jungle trekking. We stuck to the paths and if had you asked me to point to where camp was, I honestly don't think I could have. I'd put that down to lacking many of the aforementioned indicators (couldn't see the sun, too few recognisable landmarks, general unfamiliarity with the terrain).