I don't disagree with you but those kinds of packages are not going to come in Amazon boxes with Amazon labels. Also, if its possible to redirect an Amazon shipment to the correct person of course that is a very nice thing to do.
However, nice thing to do vs legal requirement is not the same. Once again, if Amazon tells you to discard or keep, that means that Amazon is going to replace the product to the purchaser. That means that if you are actually able to hunt down the purchaser and give it to them, that they are going to get a second shipment from Amazon. In other words, they will get it twice.