> As a practical matter, "what's the right thing to do?"
> comes much sooner
> in my decision tree than "what can I get away with?"
  If you find a diamond ring on the sidewalk, you take it to police and
they see if anyone claims it.  The equivalent of looking for the
copyright owner.  If nobody shows up, my understanding is that they give
it back to you.  Tossing it in the trash so it benefits nobody would be
immoral waste, IMHO.