These analogies involving valuable physical items are way off base. If I'm walking along the street and see a diamond ring lying there, I can only assume that it belongs to someone else and they've misplaced it (because it's very valuable and, crucially, there is no way for the owner to make use of its value if they've lost possession of it). I may not have any way to locate the owner, but I still recognize that it belongs to someone else and that for me to take it and keep it would deprive them of their property (probably, I should take it to the police).
If you insist on analogies involving lost rings, this situation is more like taking a picture of a ring someone lost in the street than it is like taking the ring.
No, that's a terrible analogy, because a picture of a diamond ring is worth much less than the ring. A copy of valuable information is generally worth just as much as the original. And while no-one would care if someone else had a picture of their diamond ring, they would care if someone else had a copy of their private information.
> Sure, but your carelessness doesn't absolve me of my crime.
If his carelessness meant communicating that you could take the ring without stealing it (say placing it in the donation basket instead of his wallet), that would absolve you of your crime.
If you insist on analogies involving lost rings, this situation is more like taking a picture of a ring someone lost in the street than it is like taking the ring.