Happened to me yesterday!!, seriously, this is a point of pure INTEREST, not likelyhood.
However, if
YOU read the 777 MM you will see that you are kind of missing the point here. A SINGLE RLG/Accelerometer failure does not generate a STS MSG, but only an SMT. Depending on the individual airline's policy, SMT's are generally only checked during, yes, SCHEDULED Maintenance, not on the ramp, so it is not inconceivable that a single failure remains semi-dormant here. (Witness the QANTAS incident in August 2005).
I'm waiting for some info' from Honeywell which, as I said before, may blow my arguement out of the water completely. (eg, are the RLGs/Accelerometer triple axis units maybe?). Either way, this is a fascinating debate, but none of us should ridicule the possibility of multiple case failures; much grief and headaches have been caused by such things in the past, nomatter how unlikely they may seem.