Have you ruled out the possibility that it is someone in your household that 'stole' your card? You didn't say your wallet was lost/stolen but it had your secret question answer to BB, isn't that a clue that it was someone in your HH who had access to your personal things that did it? For anyone to change your PW and PIN, they'd have to log in to your account first (if AXP saw that the change of PW and PIN was made at your IP address, you're SOL) so if you saved your ID and PW on your home PC or phone, you made it easy for the thief to access your account. If you haven't ruled out an inside job, start investigating now especially for people who knows you have a BB account and it has funds you're saving to buy a car.

AXP team said you have the right to view the documents they relied on to come up with their decision. Ask for a copy of that and if withdrawals were done at ATMs near you or the PW and PIN change were done showing your IP address, it's more than likely an 'inside job' in your HH. I have reasons to think AXP saw all these information that made them come up with their decision.

Some lessons we can learn from this:
1. it isn't a good idea to let a huge amount sitting on a prepaid account when we can w/d and transfer to a more secure bank account. Another option is to use it to pay a debt since BB has checks that one can pre authorize and we can even send it to ourselves.
2. it is best for secret questions and answers be memorized and not written anywhere; if that's impossible, codes should be used by the individual so that they're the only ones who can decode what that answer pertains to, and ONLY shared with someone your trust completely.