Well, apparently I got someone's returned Christmas present. Because when it arrived today and I pulled it out of the box, it felt kind of heavy. And when I opened it up, there was a brand new men's Seiko watch in a padded gift box in the compartment. (Also a Christmas card and an empty Macy's gift card envelope.) I looked up the watch, and it looks like it retails for about $300.
Do I assume that this is a surprise from out in the ether? Or do I call Amazon.com to find out whether someone mistakenly sent the watch his wife gave him for Christmas back with his camera bag and has called them frantically trying to track it down?
ETA: Have Done The Right Thing (TM) and called Amazon.com. They are looking into it. I just hope that if they make me send the watch back, they give me a rebate on the backpack that obviously was shipped to someone else before it came to me!