You obviously had given your QF number to BA at some stage.

BA's computers remembers the first number you give them irrespective of whatever you do afterwards.

The only thing I can suggest is to get QF to 'delete' the miles on your QF acount as well as give you a letter rightly stating so so that you may provide the information to AA. Does your boarding pass say AA? That should be enough proof of your intentions plus the letter that QF is to give you to forward to AA - but make sure you talk to them first.

Good luck.