You were not there to observe how the animals moved and there is a huge problem with basic logic. The first batches of the things which turned up around 1960 numbered in the tens of thousands. The things are very ornate and a lot of work would go into producing ONE of them; NOBODY is going to go to that much work and trouble on pure speculation, i.e. before it is known whether honkies and gringos would actually pay money for the things.
Somebody trying to start up a business like that would produce two or three of the things and see if they could be sold and then, if they could, try to figure a way to produce the things in larger numbers.
THAT however would leave obvious traces. There would be at least two or three entire villages whose entire populations had gone for at least a year or two doing nothing other than producing Ica stones. It would be very easy for Farmerman or professional skeptics like Michael Shermer to find one or two of those villages, interview people, and put the entire subject to rest. Ask yourself why that hasn't happened...