Harvey: I am sure you are right, that it will turn out to be some very simple mistake or accident, but I am betting that it will also be something very quirky or unlikely. the JMT junction sign was replaced last year, pointing all the arrows in the correct directions, and John has summited six times now over the past 30 years, so a misdirection at that point seems improbable. The Consultation Lake diversion is also possible, but the outlet stream goes right to Outpost Camp and the access trail goes back the the MWMT. I can't think of any other search even over the whole length of the trail that has gone on this long.
People rarely hike together for 30 year if not married, unless they have similar hiking speeds and styles. So this fellow was definitely way behind his friends GOING DOWNHILL. There must be a reason. I keep going back to the adage "if you are ill at altitude, it is altitude illness until proven othewise". I don't think people really appreciate the effect of removing oxygen from the brain, in terms of brain function. He may not have seen the sign, or even the junction. He may have been following the right side of the trail. Beck Weathers told me of doing something like that when his vision started failing.
He's got to be SOMEWHERE. But I find it hard to believe it is in the 2-1/2 mile section.