Stuffy,
When I saw the FAA report I concluded the same. However I did not consider a slow decompression.
Effectively the aircraft could be anywhere within a large radius.
Stanford student's theory on disappearance of MH370 goes viral
This has been discounted before. (1) Boeing said this particular airframe was not fitted with the specific SATCOM antenna installation that is the subject of the AD, and (2), it would not explain the cessation of ADS-B transmissions.
EDIT: I guess the third point is, the AD is from september and requires inspections, but only becomes effective in April 2014. This means the FAA does not consider it urgent. (Not to mention the nonsense of people becoming unconscious at 13,500 ft.)