I know it is making some assumptions, but if he were wiithin the normal trail area, wouldn't it have been likely that he encounter another trail, and not have to continue walking through 4 feet of snow and decide after a while of it to ditch his snowboard? Seems like he went "out of bounds" so to speak, although they do not spell it out.

After his fall, he just got lucky. Does not seem like his survival with all his fingers and toes can be attributed to much more. It's good to be lucky.