It's an interesting thread possibility.

Two more examples of misattribution/forgery are the Haydn/Hoffstetter

(err, bizarre visual - I guess I'd better watch it all the way through to make sure it doesn't get risqué, lol!)

And the famous Albinoni Adagio: -

The history of it is fascinating: -
https://en.wikipedia.org/wiki/.....in_G_minor
I would guess that on balance the likelihood is that there was a fragment but it was stolen and Giazotto didn't want to pay up. Otherwise it would be pretty good for a one-hit wonder.

For what it's worth, which is little
"However, a discovery by musicologist Muska Mangano, Giazotto's last assistant before his death, has cast some doubt on that belief. Among Giazotto's papers, Mangano discovered a modern but independent manuscript transcription of the figured bass portion, and six fragmentary bars of the first violin, "bearing in the top right-hand corner a stamp stating unequivocally the Dresden provenance of the original from which it was taken". This provides support for Giazotto's account that he did base his composition on an earlier source."

Err, easier on the one hand, and harder on the other because there's so much more untruth concealing the truth. There are also psychological pressures and costs of many kinds involved in uncovering more sensitive truths.

Does that answer your question?