Being a big fan of 406 MHz PLB's (yes, I have one) I thought about that very thing. The troop members were never in a life-threatening situation so it would not have been appropriate to set-off a PLB signal.
Here's another way to look at it. If they had a 406 PLB, which I would recommend, the fact that they didn't set it off is really an indication that this was not a serious situation, so nobody has to panic. One nice feature of the new SPOT device is that OK button, perfect for such a situation.