Was Kaloterna 'disappeared'?

Egyptian mummy mask excavated at Saqqara

Paul Barford has written on the Kaloterna collection that once (allegedly) possessed the Egyptian mummy mask discovered at Saqqara and for the time being in the St Louis Art Museum (SLAM). He raises an uncomfortable possibility for the curatorial team at SLAM:

One might quite legitimately ask, whether there is a possibility that Kaloterna was 'disappeared' by the Socialist Federal Republic of Yugoslavia's State Security Apparatus for political reasons.

I am sure that SLAM officials would not wish to be seen to have gained an object that could have been released back onto the market by such a means.

Did the SLAM rigorous due diligence process explore (and eliminate) this possibility?

My own position is that I think that it is likely that the Kaloterna collection is fictional. No authenticated documentation has yet been produced through the due diligence process to show that it existed.