Thanks for the links. In both cases, it seems a case of Scouts "being prepared".
I have lots more information on the first incident.
I worked up information at the time, but apparently got distracted, and never posted - thanks for the reminder:
(9/18/2010, six scouts & 2 leaders, Pine Mountain Wilderness, Yavapai County, AZ -
low on water, used ham radio to get the word out).
Here are two more news reports with more details -
the first one includes the tidbit that the helicopter spotted the signal mirror flashes when about 5 miles out.
A Scout leader friend of mine, who helps organize that event in Arizona, interviewed the Scout leader involved afterwards and passed some additional information on to me.
The Scouts were out for their annual mountaintop to mountaintop signal mirror signalling event,
Operation On Target, an annual event since the early 1980s, in which I've participated since 2009.
So, the scouts had lots of signal mirrors with which to signal the helicopter, and were practiced in their use (which is important!)
Since ham radio is used for peak-peak coordination during the event, they had more than one of those, too.
Per my friend, what caused them to be running late was that the trail signs had been removed, so they were bushwhacking their way in the heat and altitude, and a couple of the boys were getting dehydrated and short on water.
Compounding the issue is that the cell phone they'd been using for GPS had run out of juice on the way up, so they didn't have good GPS coordinates to report.(Allowing batteries to run out is a common theme in many of these incidents).
The GPS coordinates they transmitted to the Prescott ham (who relayed to the helicopter) were the GPS coordinates for the peak they had signaled from earlier in the day, which they had prerecorded, so the signal mirrors were really key, here, since the GPS coordinates they gave were only enough to get the helicopter to the general neighborhood.
Since they didn't have a common radio frequency with the helicopter, all of their radio communications with it were multihop - they only spoke to the Prescott ham directly, and he relayed from there.
The assessment of the Scout leaders in the field at the time was that they'd make it out on their own, and they just asked the Prescott ham to let their families know they were okay and running late, but apparently there was enough concern that the sheriff mobilized.