Steve,
This opinion coming from a non-fighter guy, but a guy who has worn the mask almost my entire career (3800 hours), because the gunpig is unpressurized.
I think the answer as always is "it depends"...
First, was he hypoxic because of lack of oxygen or because of other contaminants in his bloodstream. As I recall carbon monoxide bonds with hemoglobin 230 times stronger than oxygen so simply dropping the mask may not be a simple recovery solution. There are too many unknowns to kn ow the actual situation.
Second, A lot depends on his altitude at the time of the incident. As you know the higher you are the less time you have to react, and in the high 30's you may have less than 5 seconds of useful consciousness.
Hypoxia is nothing to fuck around with. I can tell you I had an IFE in OEF where multiple members of my crew began to experience hypoxia symptoms as we climbed unpressurized to our combat altitude. The aircraft had just returned from heavy fuel cell maintenance. We just crossed the fence and were climbing to altitude when folks started complaining about an extreme fuel smell. Our bold face tells us to have everyone get on the hose and go 100% oxygen...we were already on the hose and within a few minutes several of my guys started experiencing hypoxia symptoms. It took us a few minutes but we determined the oxygen hoses were mistakenly soaked in J-8...I was faced with a dilemma but I order the crew to drop masks (against the Dash 1), and started an emergency descent to 10K. I got lucky and judgement carried the day.