You make some good points, this really is going to take some careful judgment and chances are it's too complex for an actual courtroom to yield an ideal outcome.
Now places like Flea markets have been known to have a counterfeit DVD or two.
And there is more than one way to compare to non-digital content.
Regular books and periodicals can be sold out and/or out-of-print, but digital versions do not have these same exact limitations.
A great deal of the time though, just the opposite occurs, and a surplus is printed that no one will ever read, and which will eventually be disposed of.
Newspapers are mainly in the extreme category where almost always a significant number of surplus copies are intentionally printed.
It's all part of the same publication, a huge portion of which no one has ever rightfully expected for every copy to earn anything at all, much less a return on every single copy making it back to the original creator.
Which is one reason why so much material is supported by ads. Even if you didn't pay a high enough price to cover the cost of printing, it was all paid for well before it got into your hands.
Digital copies which are going unread are something like that kind of surplus. If you save it from the bin you should be able to do whatever you want with it either way, scan it how you see fit.
You just can't say you wrote it. That's what copyright is supposed to be for.
Like at the flea market, when two different vendors are selling the same items but one has legitimately purchased them wholesale and the other vendor obtained theirs as the spoils of a stolen 18-wheeler.
How do you know which ones are the pirated items?
You can tell because the original owners of the pirated cargo suffered a definite loss, and have none of it remaining any more.
OTOH, with things like fake Nikes at the flea market, you can be confident they are counterfeit whether they were stolen from anybody in any way or not.