Hi! I'm not a historian, but a biologist who spent some time in Madagascar and love the island. Since no one has answered, I'll give it a stab with what I learned, but if it doesn't qualify as a top comment, I apologize and mods please remove it.

Madagascar is a really interesting island because it is believed it was only settled sometime between about 200 BC and 300 AD. And that's pretty strange, since at it closest point it is only 90 miles from the African coast. What's even stranger (which you address in your question) is that the first settlers, based on archaeology and some genetics (if I'm remembering correctly) were Austronesian!

But over time there were also Arab arrivers, as well as Africans. This mix of cultures can be seen throughout Malagasy language, modern culture (dances, festivals, religions, food, etc), and physical characteristics.

So what time period are you asking about? When it was only the Austronesians, or any time after? To the best of my recollection and some quick fact-checking, not a lot is known about the people on the island between the first settlement of Austronesians until about 700 AD. Some historians believe the other groups came before that, to various sides of the island, and moved up and down and up into the highlands in the center and become more or less the "Malagasy people." Other's believe it wasn't until 6-700 AD that the Africans and Arabs come to the island and become integrated into the culture.

But by 6-700 AD, trading had picked up in the world. The oceanic silk road, spice trade, and slave trade went through the Indian Ocean and stumbled upon Madagascar. There were trading ports set up along the coasts by the natives for these ships. Back to my later point, most historians seem to think that this time between 600-1100AD is when Africans and Arabs came to the island and integrated, but it's hard to know for sure.

So, to answer your question: it doesn't seem so. Archaeological evidence shows people arrived around 2,000 years ago, but there is no real sign or evidence that I've ever come across that those people returned "home" with news of this island, and it remained Austronesian, isolated, and relatively unknown until 6-700 AD.

EDIT: I don't really have sources, per se. This is knowledge that I gathered from talking with Malagasy, things that were briefly mentioned in ecology/conservation texts, and I refreshed my memory and facts with just a few wikipedia pages about the history of people on Madagascar. Again, if this doesn't fit the criteria well enough, delete this.