I'm not clear what FFN was on the reservation/boarding pass - was it MH? If so, why would it have credited zero there...? Nevertheless, you will need to make sure that it has not credited to another programme before claiming to BAEC. If it has credited elsewhere you'd need that reversed - if that MH "credit" is where you accidentally sent it you might even need that reversed even though it was zeros. Probably easiest to just submit another claim for the miles with the right info rather than trying to correct the inaccurate one.