This was a silly, unprepared answer anyway, just like the order to shoot them down. They've probably setup radio scanners and possibly jammers in order to intercept the video/command stream.
With radio triangulation that should be able to pinpoint the controller. I know most of the newer control equipment is using spread spectrum and frequency hopping, but I imagine that is a solvable issue.
And they have to proceed to that point quickly enough to find the fellow operating it still there. Also, if I wished to avoid detection, I'd set up a transceiver linked to a data GSM connection and leave it in a random place in the middle of nowhere. Maybe even I'd have a few of those to confuse direction finding attempts (not sure how feasible that is).
Well, I would hope every nuclear power station has a rapid reaction security force on hand 24/7 the could respond to these 'threats'.
As for the misdirection, using cellular relay devices is something most wouldn't do and even if they did it would provide a lead that could be followed.
With radio triangulation that should be able to pinpoint the controller. I know most of the newer control equipment is using spread spectrum and frequency hopping, but I imagine that is a solvable issue.