May have heard of it, sounds familiar.
Even if they ask some Incas, and there are some left here and there, they don't have much to say about the old days, but it is possible that the Spanish didn't get everything and that there is some documentation left but is being carefully guarded. Don't know, but heard some speculation recently; it is possible, anyway.
Hans Conried is absolutely wonderful as the radio announcer.
There might be some stuff the Spanish didn't burn. Heck some of the languages are still unknown. Also all the tribes/people in North, Central and South America who used material to write on that deteriorated over time is missing as well. There may be something explaining something different. I don't know.
I do remember that they don't know why the toys (if they were toys) had wheels, but that's the extent of it. The last abstract I posted just the link to is probably the best explanation of the development of the wheel and why it wasn't developed in the New World.