The disposition of your case is still public record. A dismissal means that you weren’t convicted, but the dismissal still appears on a CORI report (Criminal Offender Record Information). Every charge for which you are arraigned will show up on a CORI unless it's sealed. I recommend speaking with a criminal defense attorney to help you through the process.
Sounds as if you requested a dismissal and perhaps a 17(b) reduction per 1203.4. If so, everything that occurred in your case is still of record. There is no such thing in CA as a true expungement.
The above is not intended as legal advice. The response does not constitute the creation of an attorney client relationship as this forum does not provide for a confidential communication.