It's pretty widespread knowledge in the spares industry, and I should think the investigators know it as well; the shady operators usually move in different circles, because the larger customers for spare parts have Quality departments who can sniff out a supplier with insufficient standards.
Panaviation have caught a lot of people out, I think because most of their stuff was good, and legally theirs to sell. The problem seems to have been with the stuff that was (allegedly) stolen back in '95, and the six A300's -worth of used items that they were passing off as new. It's very difficult to establish the provenance of non-traceable items like nuts and bolts, because they don't carry serial numbers, like the larger parts do.
If an item's been purchased in good faith, under the regulations in force at the time, then suppliers should have nothing to worry about. They may have to refund their customers' money if it can be proven that a part is not what it is claimed to be, but if someone's daft enough to pass off an obviously (to the naked eye) used part as new, then they deserve all they get.
Believe it or not, standards are immeasurably higher than they used to be!!!