Good luck in your quest and recover of the map. But as Phil and Ralph has stated, not much anyone can do without pictures. And that is only if the person who took the map tried to sell it. But from what I gather, since they took only the map, it looks like they have other motives than profit/selling it so very probably it will not see the light of day unless you recover it directly from the person.
And if you do recover the map, is this wreckage in such a remote location that it is likely not to have been found already after 70+ years? If the pilot managed to land the plane (albeit perishing in the process), I would assume it was in an area that would not conceal the plane. And is the map a guide to the location of the plane? Or just a standard map with a dot? (i.e. who put the "dot" on the map and what does it represent).
I'm sure you have thought all this through and know more than what I have read. So, don't take this as a dismissal but more of query.
Also, if you have his other medals and dagger, we would love to see them.