100% not true! Although as you mentioned I think the seller proved they aren't the most knowledgeable about the book by stating only 12 copies exist.
Further, there is no way Marvel would do a RHK movie before a TGK movie!
I think they should do a movie with the big three, Kid Colt, Rawhide Kid, and Two Gun Kid, and call it the "Mighty Marvel Western" If it was a little gritty, still PG with a great story line (see opposite Jonah Hex) I think it would be a winner. They don't seem to be able to make a great western that will work for today (see Lone Ranger, awful). I know it could be done, heck all of us could probably write a much better -script than the garbage coming out of Hollyweird. Charlie Hunam (Sons of Anarchy) as Kid Colt? Stan as the saloon bartender, or the old gold prospector? It could be done right.............