I would contact ORD as BA's agents will pass them to the lost property, you will need to provide the seat you where sat in

claim on your travel insurance, and get some nice new QC25's if you get no joy.
This is the page to go to which lists who to contact:
http://www.britishairways.com/travel...gb?p_faqid=531
Open the PDF that is linked to and your good to go
Im sure you will see your Bose again...