Originally Posted by HomelessScientist
Not necessarily -- the pilot emergency oxygen system is completely separate from the passenger overhead mask system. Also, there are portable oxygen cylinders for the crew stored in the galleys.
If the pressurization fails, atmospheric pressure at high altitude may be too thin to allow the lungs to inflate, but I believe this is more an issue at 60,000ft then 30,000. Reviewing Payne's NTSB report, it notes that the oxygen system on board was not rated for above 40,000ft (the plane was at 45,000) and that prolonged operation at 35,000ft was not recommended.
I wonder if the pilot's O2 system either failed or the pilots exhausted the supply (possibly by staying too high for too long and not descending to 10,000ft) and the other pilot referenced in the SMS message was attempting to grab some of the emergency/cabin crew O2 canisters when they were overcome by anoxia (assuming it was a problem with the oxygen/pressurization system).
There is a cabin pressure alarm on the 737. If it was working properly, then it would have sounded when the effective cabin altitude went above 10,000 feet, no matter how slowly or how rapidly the depressurization happened.
Obviously at this point we're at random speculation, but the sensor may have failed or been deactivated, or the flight crew failed to head the warning until it was too late.