I imagine that if kids took it and saw what it was, probably worthless to them, that it could have been just dumped too.
That was so rude of your neighbor! Some people just don't care about anyone but themselves.
I was getting mail from Social Security that was one number off from my address. It looked like a check and I thought someone might really need that. Even though the houses next to me weren't that number either (they aren't sequential for some reason, there are gaps in the numbers) I went to my neighbors asking if it was theirs. It wasn't so I put it back in the mail with "not at this address" on it.