Maybe it was caused not by corrosion but by cosmic rays
They are apparently looking for them as a possible cause for the a330 incident off WA so why not this one.
ATSB probes 'cosmic rays' link to Qantas jet plunge - The West Australian
The reality is that if they can't find the bottle(s) then how can they ever say what caused it with any certainty so I think this is one for the TV Mythbusters to do an episode on.
The results will be just as conclusive.