probably line of site considerations. If he made the call from a valley or gully somewhere, he could have line of site to the sattellite, but any direction finding stations would be shielded from line of sight by the moutains or sides of the gully. See Clancy's "Red Storm Rising" for an example of such a technique. Of course in Clancy's story, it's the good guys (USAF & USMC) using the sattelite phone, while the bad guys, (Soviets) might be trying to RDF on them. It would be even easier to do in Afghanistan, since it's not all that far north, compared to iceland anyway, and any geostationary sattellite would be fairly high up in the southern sky, meaning the valley could have pretty steep walls.