if the bank made a copy of a one of their coins to service an apparent withdrawal, but that copy was never 'spent' then the original is still good.
Hmm? What's an "apparent" withdrawal? The bank's transfer to a depositor is the same as the bank "spending" the bitcoins. The transfer is a transaction that will be confirmed by bitcoin's peer-to-peer protocol. After the transaction the "original" is not "still good" and cannot be spent or transferred, i.e., will not be confirmed by the network.