They were deep in a trail-less canyon. Maybe they tried to scramble up the slopes. They also could have back tracked and ended up southeast of the Maze Loop wandering in circles through the rock canyons thinking they were close to the Loop. They did minimal searching of that area and most of that was done by helicopter.
In 2010 Edward Rosenthal was lost for 6 days and travelled 20 miles before being found.
I just read an article on Edward Rosenthal and he was missing near the end of September under high cloud cover. He was also an older gentleman and it was still in the 97-99 degrees range but he was aided by not fighting the incredibly brutal sun that these two folks had to deal with.
I could be wrong. But I still think they were met with some sort of foul play. Perhaps someone knew of their hiking plans and set the scene to make it look like they were lost.
I also posed this question but I don't believe it was answered.
Were their tracks of walking in circles over a large area? Are we talking a half a mile? A couple miles? Ten miles of tracks? I think that's important to narrow it down to whether or not there could've been foul play. Were their any signs of a struggle? How long could the dogs follow the scents?
I apologize if these questions have been answered already.