I've only seen one and it was under construction by a flint knapper, bowyer in Northern Wyoming. Testing was done at the Cody Firearms Museum. They're a recurved bow, similar to Mongolian ones. No wood, just plys of mountainsheep horn glued with mountainsheep hoof glue. Really thick at the grip but not long. If every Indian in America had had one in the 17th century we might be Euroweasels ourselves today. As it was, the Arapahoes guarded the secrets of their construction zealously and there just weren't that many mountainsheep.
" If every Indian in America had had one in the 17th century we might be Euroweasels ourselves today."
Interesting thought, but it's my understanding that disease played a very large role.
Look at the Pawnee -- they never had a war with the whites, but by 1900 there were only about a thousand of them left.
In 1849, I think it was, cholera wiped out half the Southern Cheyenne at one fell swoop.
If the whites had been more patient, they probably could have "sicked" all the Indians out of their way.