It’s tempting to look for potential vocab exchange between Rapa Nui and (Quechua and Aymara). That could help dating the exchange with the Andes, as the lexicon stops following the lender’s sound changes to follow the borrower’s instead.

(Polynesian syllabic structure and small phonemic stock make this extra tricky though. For example, Classical Quechua /s ʂ h/ would probably end all merged into /h/, and you’d see multiple epenthetic vowels popping up.)

Even then I wouldn’t be surprised if they contacted the folks up south, like the Mapuche. Specially as I don’t expect the landing spot from a Rapa Nui → South America to be the best spot to start the opposite travel, due to sea currents.

Check out the podcast Fall Of Civilization episode on Rapa Nui.

https://fallofcivilizationspodcast.com/2019/07/26/episode-6-of-fall-of-civilizations-is-now-live/