Not all missing people stories have a happy ending. I have a relative who's been missing since Sept. 16, last seen in Riddle, Oregon. More info at http://findmark.org. We recently realized that he had his iPad with him. If you have any ideas on how we could use it to find him, I'm all ears.
I assume you've already checked this, but just in case you haven't: is Find My iPad setup? If so, and if you can get access to his Apple account, then you can track it that way.