I'm pretty sure the lawyer has signed the duplicate that is in his possession. Technically, the contract only has to be signed by the party against whom enforcement is sought. If the percentages are not filled in on the one signed by the client then the contract is incomplete and may be voidable. However, a client can terminate a contract with a lawyer at any time for any reason.
DISCLAIMER: This is not specific legal advice and does not establish an attorney/client relationship.