Hawaii was populated. It seems to be more isolated, so the only thing differing is the stupidity of the protohumans. That would seem to be an asset in this case. There would be a dullness to the perception of danger and unless they paddled with one extremity, causing them to circle aimlessly, it would be inevitable that heading "south" would cause them to run into Australia. As to the lack of fossils, the standard answer is operant, they haven't been found yet. Still, I like the airborne dispersal theory the best and as the Hawaiian Rock Wallaby shows, you don't need no stinking 400 badges er.. specimens, three will suffice.
Hawaii was populated, true. Obviously so. But we need to keep in mind that in the case of Hawaii, which was populated late in the Pacific expansion, that those that did "it" had extremely good sailing skills. Surely it wasn't populated strictly by those on the first voyage. In other words, hundreds of people didn't set out to populate Hawaii right off the bat. Exploratory voyages, following bird migrations, often took place, and that's how most of the Pacific islands came to be populated. Once a landfall was made, those who did the dirty deed then went back to the Marquesas (sp?) and told others what they'd seen and found. Then a much larger voyage, encompassing many more people left for the new lands. Kinda like Columbus.
Please recall that the first voyage in 1492 was with only 3 ships. The second had a much, much larger number, and many more people. Can't recall off the top of my head how many ships or people. But more. I certainly recall that.