Legal Question in Real Estate Law in California

Unless specific offer and acceptance conditions and terms are included in the offer, a signed acceptance of a contract is generally deemed complete and delivered once it is deposited in the mail. So the contract is almost certainly fully enforceable.

If you received a fully executed Purchase Agreement from the seller signed by all parties, BEFORE seller notified you or your broker of canceling it, it MAY be possible to TRY to enforce the contract. If you are willing to incur the attorney fees, court costs and delays involved in that process, without guarantees of success,I'll be happy to help you. Most people would likely accept the cancellation as a reality and look for another property.

Generally the broker is the agent ( presumably for the Seller, though you were not specific - it matters). If the broker represented only the Seller and the Seller directed him not to deliver the documents and not to proceed, he should not have done so. If the broker represented both buyer and seller, things get tougher. If the documents were delivered to the Buyers Broker ( who represents the buyer as the buyers agent), you have a contract. We need more facts.