I personally think your third possibility is the least likely. I just find it unimaginable that there would not have been any cultural exchange at all of the two peoples knew about each other.

I can imagine human beings, even extremely capable ones, just missing things. In fact that happened a lot. There were many European cultures that had the technical capability to sail to the Americans for thousands of years before they did it. And there were clothes in the Americas that had the capability to go the other way, but they didn't.

As someone else pointed out, there is a similar story for Madagascar. There were plenty of cultures that could have discovered it for centuries that just didn't. Similar stories with countless other islands.

Honestly, I think it's more surprising that the indigenous Australian peoples discovered the continent when they did. They were the only animals to make the jump across the straight.