The excellent book by Ms. Boskovic seems to be an outstanding reference, and I wish I had a copy! It is interesting about the reference to Baron von Trencks memoires being a forgery, but as sensationalized as his case was in the times it does not seem surprising that such things would occur.
What are a matter of well established and documented fact are the descriptions of the exploits of his units of pandours, which as noted were disbanded in 1749 as he was imprisoned. It is important to note that these troops under his command were assembled from mercenaries that were comprised of numerous ethnic groups from various regions. They were an essentially privately assembled force of irregular troops who obviously would have used thier own weapons, though acting as auxiliaries for the Imperial Army of Austria.
Since these troops were essentially private and operating outside the regulatory standards of the army, it seems that it would be impossible to determine exactly what weapons were used by whom, and they were using all types of weapons from regions which had been under Ottoman suzerainty.
There were of course yataghans of Ottoman form used throughout the Balkans, including Croatia, which comprised the larger component of von Trencks forces. Since these troops essentially became outlaw, it seems unlikely provenanced examples would have been reliably documented.
While I would not question the well established authority of this very esteemed author and curator, I am admittedly a bit surprised at the assertion that no yataghans were in use in these regions, thus presumably could not have been used by von Trencks pandours. This would be like saying that the 'trench gun' shotguns were not ever used in Viet Nam, since they were outside regulation .
It must be conceded that a great number of the weapons that are believed to have been used by pandours, particularly the horsemen,often had heavier deep bellied 'yataghan' blades, and typically European style hilts or in many cases karabela or shallow yataghan eared types, along with of course varying European style sabres. The foot troops, however, seem to have in some degree carried the more familiar yataghan as a secondary weapon in the sash in janissary fashion. It seems I was once corrected in my assumption that Balkan or European forces fighting Turks would not have also had yataghans
some years ago.
The attached map is to illustrate the proximity of these regions, and the likely potential diffusion of the yataghan, as well as a couple of the illustrations illustrating 'panduren' and are probably among those being disputed....and our man in question, the Baron.