I am not a RF engineer and only an amateur pilot but I feel fairly confident in saying:
RF interference on internal inter-system aircraft communications would require power output well beyond your average mobile phone to make any impact (especially on digital systems which generally cope better with background noise and random signalling errors than analog systems).
In order to influence signals on digital circuits, the RF signal would have to be powerful enough to significantly alter the voltage on a wire at specific intervals.
As a very crude ad hoc experiment, you can open up your home computer and place your mobile in there and then call it and text it repeatedly. See if anything odd happens on your computer. You may get the characteristic GSM warble on your computer speakers and even on the screen (if its analog) but the computer will happily keep working. With nearly direct contact inside the computer, the phone is posing much more RF to the computer's unprotected internal bits than a passenger's phone several feet and surfaces away from aircraft systems and wiring. That and hopefully the 777 uses more resilient hardware and software than your average Windows XP computer!
If RF issues did occur on BA038 and assuming the proper instrumentation in the logging systems, there would be something similar to erroneous CRC errors and other such "bad value" errors.
More of a concern would be RF from outside the aircraft, a concentrated EM pulse for example.