You should be using getreceivedbyaddress rather than getreceivedbyaccount. You didn't assign that address to any account.
What theymos said. You're asking for the balance of the account named '1Fs5rqB2sXZ3kax1r3HfuYpK2ksSxLYJT8', and there is no such account.
Whether bitcoin should return an error (instead of 0) if you ask for the balance of a non-existant account is debatable...