Actually, if decompression happens, what happens is that you have a few seconds (roughly 18 seconds at 40,000 feet with heavy activity) before loss of consciousness. That's why the pilots are equipped with quick-don oxygen masks that they can slip on in a matter of 5 seconds or less. So if the plane suddenly decompressed, the pilots still had more than an adequate amount of time to don the masks. (If you add the time for reactions and such - typically about 1-2 seconds to recover from the shock, another 1-2 seconds to identify the problem and to realize the solution, then another 1-2 seconds to grab the mask), it still leaves a bit of time.
Of course, who knows what really happened, though. Just that an explosive decompression does not lead to instant unconciousness.