I went to bed on page 29 and woke up with 20 minutes of reading to catch up!
All the research has been wonderful here and hopefully it is the correct family you're following
It is difficult to understand how some one could leave a bear and a photo
and not have worked out by now where they may have left it
unless this poor bear was not wanted??

I wonder was it a gift to a visiting relative after a funeral perhaps?
that was graciously taken but then abandoned?
If this is the case he/she may never come forward as they would have to admit to this!!!

Or could it have been a gift that was never officially exchanged at the airport?
Then person giving the bear away may think the new owner has it
and the intended new owner is oblivious to not having it??
Anyway I am in agreement with a comment earlier there is a novel in this
a modern Paddington Bear shall emerge, or maybe another Importance of being Ernest?!
Great work everyone - waiting for next chapter!