That's a good assumption. Have you ever heard the old radio show The Report on the WeUns which was a CBS Radio Workshop from 1956. It's the supposed broadcast of some archaeologists from mars exploring earth in 7956. I don't know if it's available on line. If not your local public library may have it. I really like it when they explore the great temple to the great god May C. It's like opening King Tut's Tomb.
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.