I've been thinking a bit more about this. It's not uncommon for people to build up thousands and thousands of miles that they are unable to use - my boss is exactly that, so I know he regularly lets other people use them - which is fine and within the BAEC rules - I think there is probably some rule that states you can't sell them but if this guy is an exec member, why would he risk this and chance not only losing his miles but possibly being banned from BA and criminal charges. If there was a genuine miles booking in BA's system- he had to have enough miles to do it, ie. he couldn't have held a booking just to do a scam (you can't hold a mileage booking whatever your status with BA)
Therefore in order to pull off this scam it would have to have been a full fare booking that was either paid for and he was going to get refunded or held till the advanced purchase kicked in. This is all very risky to try and con someone because BA will have loads of details and info on him that could be passed to the authorities if necessary.
It could very well be a simple error on BA's part, either with their sytems or ticketing, especially if the booking was made by an outsourced centre like Jacksonville.
You definately need to speak to someone at BA in the UK - try and get someone sensible with common sense and a good tip - if you try and speak to a manager and explain it you might get somewhere. I am sure if this is a scam then BA will want to know about it to stop it happening again.
Again - Good luck