coin seems to have gone to a duplicate address
bitcoind (and hence presumably also americancoind) keeps a separate database of "relevant" transactions so that it does not have to search the entire blockchain all the time.  Since you added a new address by copying wallet.dat, the daemon may never have figured out that transactions involving that address are relevant.

Try rebuilding this database with americancoind -rescan.  You can also try americancoind -reindex to rebuild all databases (this may take a long time depending on the size of the blockchain).

It's extremely unlikely that someone else managed to generate a private key with the same address.  If this were at all feasible, the currency would be useless.  Moreover, even if this had happened, what you should see would be your transaction sending one coin to Azpv... and then another transaction created by the attacker, sending the coin to an address controlled by him.