while I do not know the particulars of this airplane, it is possible that the oxygen system is gaseous (big giant cylinders and plumbing) rather than oxygen generators.
perhaps someone out there in internet land knows for sure about this PARTICULAR plane.
and an excellent point golfyankeesierra about once using the oxygen, you have to go down to lower altitudes just in case.
wondering too about exact location of turnback and if Santa Barbara might have been a better choice for emergency landing (shortish but ok runway), former Point Magu NAS etc if they were actually thinking about San Nicholas Island NAVY OLF.