He never used the hash of any Sartre quote (that was just misdirection) - the double hash that he used was simply that used in Satoshi's tx along with the signature that was used in the tx.

(basically he just copied and pasted from the blockchain then put together an elaborate pretense that he had somehow managed to sign something else using a private key known to belong to Satoshi)

Even the silly BBC report has been corrected once they finally worked out that they had been tricked.