The Telegraph of Calcutta is running this article, including this bit:
the Assam chapter of Indian National Trust for Art and Cultural Heritage (Intach) has disagreed with the report, saying Koro was not an unknown language in the region and linguistic experts were aware of existence of the language, adds our Guwahati Bureau.I have no idea what the facts are here, and it doesn't change the actual situation in substance, but it seems plausible that local organizations in Assam would have known about the language. Happily, at least we can be pretty sure that this won't become a Tasaday-like story.
Dinesh Baishya, the convener of the state chapter of Intach, told The Telegraph that an international conference on endangered languages of India last year discussed the language.
Update, 6:00 pm: According to this AP story, Koro is a "hidden" language, and David Harrison says that "Even the speakers of the tongue, called Koro, did not realize they had a distinct language". I'm curious to hear how that works … extremely little contact with speakers of the (apparently distantly) related language?