Why do you assume that one must knowingly throw something away for it to become the property of someone else? I disagree with that assumption. The court seems to have made the correct decision given this information. He gave explicit consent when he dumped the stuff in the trash, fully understanding how trash works. It was his duty to know what was being tossed out and failed in that duty.

I also doubt a drive from that year was so easily missed, but that's irrelevant.