@irvmull
So if McGraw-Hill prints a book that turns out to have been stolen, do they face any repercussions?
They might, it depends on a lot of factors. The following assumes US Copyright law.
The actual copyright owner (or an officially designated agent would have to file a lawsuit for copyright infringement (copyright is civil, not criminal)
The owner will have to provide the court with proof of authorship.
If the copyright is not registered, the author has to prove "actual damages".
https://patentsavers.com/unregistered-copyright-infringement-damages/
In the case of an unregistered copyright, damages are limited to those which can be proven; in other words, actual damages. This means that the holder of an unregistered copyright can recover:
Any actual damages,
Any actual profits or money lost, or even potentially lost, and
Any money gained by the person who is using the work without permission.
So, assuming a story published on (and stolen from) SOL for free, that limits damages to "Any money gained by the person who is using the work without permission".
If the real author is deceased and their heirs are unaware of the existence of the story, then McGraw-Hill is extremely unlikely to face any legal repercussions.
And even on "bad publicity" type repercussions, if the story was published pseudonymously and the real author is unable to come forward, significant repercussions are rather unlikely.