I wondered if someone had died and a family member had either been to a funeral or clearing a house and was taking the bear/photo back home with them?
Jane you mentioned a place in Bristol that deals with Steiff bears? I wonder if anyone there would be able to help by seeing if they remember or have record of a valuation, or can tell us if it is a Steiff bear. If he was not worth much (sadly) the owner might not have been bothered about trying to get him back?
I wonder if the airport keep a log of people calling to looking for something? What if the owner rang the airport before the bear was found or taken to lost property? (Although I'd expect a left bag at an airport to be noticed quickly!)
It would be really useful to know what kind of bag and other things the bear was traveling with

but I think the airport may have to keep that to themselves so that if the owner claims the bear they can be sure it's genuine?