Folks, if you have the expertise to log on to PPrune, you have the skill necessary to <i>buy</i> a cell phone jammer.
But what the heck does this have to do with the discussion at hand?
Either the thing was on board, at which point you'd have to ask: why would someone turn it on right at finals? Frankly, there's no reason that makes sense, given the other, more "sporting" opportunities that would have presented themselves before hand. On the other hand, if you want to argue for RFI, there are plenty of ordinary cell phones out there, and one in a million could -- perhaps under the influence of the right combination of overuse and tight jeans -- perform in an unpredictable and noxious manner on the wiring a few centimeters away.
Or the thing was in the environment, several miles from the threshold, and on the ground, and then you'd have to ask, "Why does this matter again?" I mean, have you driven by an airport and measured the environmental RF noise? You have more cellphones, more bluetooth devices in one area, along with several radar systems and HF/VHF/UHF transmitters, and most of these have a clear line-of-sight to the runways. Heck, I remember being in a bus passing a military airport in Syria where the noise was so bad, the entertainment system speakers started serenading us -- and they were switched off!
So, no. I don't see cell phone jammers as an issue. RFI is a "dark horse" candidate, but there's no call to get exotic here.