It's indeed possible that Trenck-mentioning envoy reports simply haven't made it ito publication. However, the Trenck/Amalie romance was really popular among late 19th and early 20th century novelists, and the debate on how much or little truthful Trenck was raged on, so I would assume if, say, an Austrian report that mentions him did exist, this would have made it into print a long time ago. Especially since the archives in Vienna were far less censored than the ones in Berlin (not just to historians; by the 20th century, novelist Stefan Zweig can look up Joseph's letter to Leopold about their sister's marital sex life or lack of same), and even in the 19th century, Austrian historians would probably have downright enjoyed publishing anything embarassing to the Prussians. Especially since the majority of German historians swallowed the Hohenzollern version of history so completely that when stuff like Arneth documenting that the "MT wrote a dear sister/dear cousin letter" tale was pure Prussian propaganda and not fact happened, it took eons to sink in (with some laudable exceptions).

(We don't have all those Seckendorf reports to Eugene about Junior's marriage plans that destroyed the legend of the evil Catholic plot thanks to Prussian archives, I don't think.)

Lol, now I'm trying to imagine handling Voltaire in a hush-hush manner.

Agreed that this would have been impossible, even if they were no witnesses to the abduction and Voltaire didn't manage any message smuggling, by the very nature of his silence.

(Voltaire: I've been locked up in the Bastille itself and used the opportunity for publicity. You think some second rate Saxon prison is going to shut me up... Luc? Do you?)