Whenever you cancel any contract you do so in writing. CAR forms include cancellation of listing and purchase contracts. You did not know that but your agent and his/her broker did.

While there are contractual obligations under the RLA the courts are very aware of the knowledge level of general consumers verses real estate professionals.

You have two places to start. The first is the DRE. Although it is a chore you can contact them and talk to them about this issue. You can also choose to file a complaint against the broker with the DRE. He is being an ahole to you. Second you can contact SDAR, the San Diego Association of Realtors and let them know what is going on. Both of these entities may or may not have some legal services for you to contact. However, they are in the business of providing legal services to realtors/brokers, not consumers.

Prior to contacting these entities call the broker and let them know you will be filing a complaint against him with each of these entities. Furthermore ask him why he never provided you a written release from the RLA and/or the purchase agreement when he knew full well you were done with his services. Let him know that after you contact these entities you will be contacting a real estate attorney to get a full range of options.