You cannot submit retroactive claims if the flight has already taken place. You can, however, have the BB# added to your pnr after purchase though.

I was able to "retro claim" on a flight, but this was because the Air France Luxembourg sales phone number transfers to France while the KLM transfers to Belgium. I bought a C TATL ticket and since they issued it from France (how was I supposed to know since I rang my local number) it was rejected. I complained and they credited it to the account.