WELL, I suffered through most of that until the end. I understand your point, your concern and your fears. I understand that you are grasping at straws to find the answers, BUT...
There were many good responses. Many that made sense and were true, some that were just preaching. However, I think the topic is played out. By bringing it to another forum I think you are just looking for the answer that you WANT to hear. There were responses by intelligent people, IT people and even a lawyer.
Perhaps someone here may find a legal loophole, but the bottom line is that the data is gone- regardless of whose fault it is. You may continue searching and not find the answer, but, by that time, your father will be done re-doing all his work. I know you feel bad and perhaps guilty, but I don't think there is much more that can be said.
good luck though.