Jet Airways — lost bag

Myself shriya modak was allotted a booking no. Saacgw at pune airport, india, as pune-abu dhabi to london to boston.
Based on the same i travelled all the way to boston. My final flight from london to boston was on ba215.
On arrival i realized that one of 4 bags, which i checked in at pune, india; was missing.
Accordingly i tried to report the same to ba customer service, who also advised me to alert all the airlines i travelled on 12th jan 2018.
I had also sent emails to all the relevant airlines customer services.
I wish to bring to attention that i was asked to submit reference no of the complaint.
To my dismay, since my journey was handled by 3 different airlines, the original baggage tag no. Issued by jet aireways is not being recognized while filing online bag missing report.
As a result, i cannot proceed any further in the matter.
Hence i wish to bring to notice what happens when your journey is handled by different airlines. Each airline tries to throw the ball in each others' court & in the end the passenger suffers.
I wonder how my problem can be resolved. My id is ([protected]@gmail.com).
Regards,