Excellent explanation, especially interesting on how old they are proven to be.
My own thought on why they are found rather randomly ( not found in a pile where a net had been or a few from a bolo ),,,some of the best have rather discrete notches, they may have just come loose and lost. Consider the quality of the "twine " that existed in that period of time,plant fibers or rather thick rawhide strips. Net weights would take a pretty hard bumping on the bottom and a bolo throw would be a really brutal treatment.