I would spend about $25 on a Case Sodbuster. About $25 on a Colt mini trapper. About $25 on a Marbles Camp cleaver/machete and buy as large a Norton combination India stone as I could find with the rest.
Note, none neither of the two listed are currently pocket favorites, but they would certainly be acceptable pocket knives in an austerity situation as described. I recently bought some 2nd tier pocket knives, getting four different knives for a total of $80.
I generally stay away from these kinds of hypothetical questions, or at least whine about them, but stuff does happen to folks that is completely beyond their control. I watched a video at church last night on the Japan Tsunami in one fairly small coastal town and the town was completely wiped out in the 9 min it took to watch the video. A lot of folks lost everything including their lives. No one escaped with more than what was in their hands and pockets. So, this is at least as plausible as some of the other scenarios we put forth. It warrants some thought.
In my choices above, I might be able to scrounge a sharpening stone for a couple bucks at the right place, or maybe a file and a ceramic coffee cup; I'd need the coffee cup for other duty anyway. This would let me buy a RR or Colt canoe, or a Case slim trapper in delrin with the other $20. Just thinking like a knife knut.
Ed J