The chances are very slim that IB+ will remove Avios from an IB+ account in order to credit you with AA miles.

Essentially, to IB the issuance of Avios for paid flights is essentially free, whilst paying AA for miles costs them money. You'd keep getting the runaround until you give up.

The lesson to be learnt is to NEVER be logged into an IB+ account when making a booking. I don't (I credit to BA) and have never had a problem.

FWIW RJ is notorious for this as well.