I believe this is right. The trade in ancient manuscripts is surprisingly cloak-and-dagger. (Edit: I base this on such vast experience as having read a couple New Yorker articles about it.)
Just curious, but how do you get in the loop on the ancient manuscript trade? It's not even an area of work I have ever thought about before.
Potentially unrelated, but I had some very brief conversations with a paleontologist I worked for a while back (working for a very respectable public institution) about black market fossil trade; it's VERY common (and often fronted through "legitimate" fossil/mineral traders) and if you're at all in the academic side of obtaining these sorts of items, you very readily run into people obtaining them for many sources, and get a better view of the "flow" of these items. I would imagine similar fields (in terms of dealing with "historical" items of value) have similar black market systems.
With how Jesus scholarship as a field has evolved and how achademia as an industry operates, it is not surprising that a "scholar" was duped.