You need to have the flight removed by QFF (email them. It's not as painful as you might think), then print out the statement to show the flight having been removed, and then write a letter to BAEC explaining what happened and ask them to credit the flight to your BAEC account.

QF will reverse the flight credit on request if you have a good reason to do so, which you have, since it was credited to them through no fault of your own.