I'm not sure I disagree with you in this specific case, but I think it's fairly easy to tweak some of the details (is there identification in the wallet? Is it obvious it's been missing for an extended period? What if it's not money, but some possession?) and vastly change the percentage of people that would respond one way or another, even when there might not really be much ethical difference.

That said, I was mostly pointing towards what I see as an explanation for the difference in attitudes regarding wealth and poverty and how it intersects with peoples opinions of personal responsibility, which I think does have a place in that scenario, even if it's not always the primary driver.