The smallest member of the rhinoceros family once roamed as far as Myanmar, India and China. Today, there are less than 200 individuals left in the world, and they are all scattered across little pockets of forest in Malaysia and Indonesia.
The problem, I believe, lies in the lack of research.
A search on the webofknowledge for the world "sumatran rhino" yielded only 24 publications over the past 27 years--that's less than one paper per year. On the other hand, other endangered species, even the lesser known species like the Asiatic lion yielded 37 more research paper than the sumatran rhino over the same period.
The reason behind all these comebacks? Intense research and investigation.
In June 2012, a calf was born in captivity in western Indonesia. It is only the fifth known birth in captivity for the species in 123 years. Vietnam's Javan rhino was declared extinct last year (2012). We don't have much time left for its sumatran cousin.