Ah, I love a nice Shakespeare pun.
I've heard back from the Royal Shakespeare Company on the very curious press release found in a Spanish publication about their working on a "Shakespeare play about a character from Don Quixote."
The project will be based on Lewis Theobald’s eighteenth century adaptation of a manuscript of Cardenio, the original source, Thomas Shelton’s 1612 translation of Don Quixote as well as the original Spanish version of the episode in Don Quixote.
So this is not an academic or literal find - but hopefully will be a theatrical find - a collaboration between Spanish and British artists to eventually bring a production to the stage of Cervantes’ story of Cardenio – via William Shakespeare – of which both great authors might have been proud.
(Emphasis mine.) So, there you go. Everybody go back about your business, nothing to see here.
I'm curious, though, about the wording in the article which said: "The piece has been lost for three centuries after a fire at the Globe Theatre, but now the Director of the Royal Shakespeare Company, Gregory Doran, has said they have managed to confirm the authenticity of the piece. It was written with the dramatist John Fletcher, and had been performed twice by the King’s Men Company in 1613." It seems to be that "managed to confirm the authenticity of the piece" is new information, more than just doing another project based on Theobald's Double Falshood, which has been done for years.
I've written back asking if they have any more to say on that particular question. Now that I see it in better context I think that perhaps the author of the article was unfamiliar with the history of Cardenio versus Theobald's Double Falshood, and wrote about it as if this was a new discovery.
Update: The official word is "there is nothing new to add to the authentication debate...some facts may have been slightly lost in translation." Gregory Doran will be working on his project on the assumption that Theobald's work is, in fact, based on the Shakespeare/Fletcher original.
Thanks very much to Nada Zakula of the RSC Press Office for getting back to me!