I have a theory that any time there's a fork in the road or trail, human beings are susceptible to what I call "the fish trap". This is the second case I've read of where people took a wrong turn on the return journey because they failed to notice on their way in that there's another path coming in from the right or left behind them.

Because they didn't make any "turns" on the way in, they mistakenly assume that they won't have to make any turns on the way out. Thus, when they come to a fork in the road (which they don't remember coming in) the natural tendency is to just continue straight ahead.

When you think about it, it's very similar to the way native americans (and probably others all around the world) used to, and probably still do, catch fish. (In fact, lobster pots operate on the same principle.)