Yeah I know , we all want it both ways, but in this case do you think it's possible?
Either you're going to have to wait for a replacement or keep the bike and fix it yourself.
BTW there should be no reason opening the motor or controller could even be detected, as long as you don't damage the screws or something.
This is a case of making a decision and acting on it.
Again , if it was me , I'd send it back, who knows what else may have been affected by whatever caused the short. Was the packaging damaged at all?
Something else to consider, if you can't get yourself to return it, you should ask for a price adjustment for the defective product. They probably have to pay for the return shipping so it may be worth it to them, to give you a partial refund.