Ok, then 7701 or 6700 or anything that was close to 7700. I`m just saying that the chances of a compos mentis flight deck flying for an hour an not making radio contact on vhf1 which will run of the battery is not plausible.
Therefore I`d go with either decompression or unlawful access to the flight deck. If no-one is claiming the latter then I`d go with the former.