...one of our legit disks went bad and we downloaded a copy. While that isn't illeage you were glad to find it.
I don´t think it´s legal, but I believe copyright
should be modified in a way that it becomes legal. You´d be a real tuna head to sue for such a copy and if I were a judge I would urge the parties to settle so that the infringer pays no more than the cost of the media & shipping for the new disk.
Law should advance to the point it actually makes sense. However AInc paid for the AmigaOS IP and they paid the one, who paid for it to the one who paid for it to get it from ESCOM/Gateway. (I am a bit confused about all the details, there may be some confusion along the way) So that is a very strong indication that these rights are not in the property of Joe Random and they certainly aren´t free of rights or public domain.