The Byzantine bureaucracy was incredibly complex and highly organized. There were certain people (usually eunuchs) who would be holders of the title “Prōtospatharios” and essentially be the head of the Byzantine bureaucracy and report to the emperor. Eunuchs were common in byz. Government as they were unable to bear children and thus would have little family ties that would cause corruption. Under the Prōtospatharios were a number of other subservient titles and these formed a complex but functional hierarchy. Byzantines however did record a great deal of the goings on in there government and records of state secrets and visits exist. The Byzantine historian Michael Psellos, himself a member of the byz. Government wrote a great deal about the operation of the government , as did emperor Constantine VII Porphyrogenitos, who literally wrote a manual on Byzantine government.

With regards to the production of Greek fire it is highly likely that its production was very decentralized and thus only a few people in the whole empire would actually know the complete recipe as the byz. Went through great lengths to conceal this so it’s not that the recipe was lost per sey but it would have been incredibly hard to find even when it was being used by the byzantines.

Psellus, Michael. The Chronographia. Lulu Press, Inc, 2015.

Skylitzes, John, and John Wortley. John Skylitzes: A Synopsis of Byzantine History, 811–1057: Translation and Notes. Cambridge University Press, 2010.

VII, Constantino, and Constantine VII Porphyrogenitus. De administrando imperio. Vol. 1. Dumbarton Oaks, 1967.

Roland, Alex. "Secrecy, technology, and war: Greek fire and the defense of Byzantium, 678-1204." Technology and Culture 33, no. 4 (1992): 655-679.