I read this story and mapped it out a few years ago, and they could (probably) have walked out the way they came. They passed a low scrubby area with a spring on the way in. I imagine most people would have simply backtracked on foot and (probably) survived.

I can only guess they had absolutely no idea where they actually were - but perhaps thought they knew where they were. That is the only explanation for continuing forwards on foot rather than turning back. If you're looking at the wrong place on a map, especially an inadequate map, it's easy to think you're going the right way when they are 'dead' wrong.