File a request for reconsideration with a copy of the proof. May not work, but can't hurt.
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Go to court and show your proof of insurance, to the same court that you went before and ask them to pull out your file or they will give you a new date to go back.
You can file a motion for reconsideration and include proof that you had insurance on the day of the violation, but please understand that the San Francisco traffic court is extremely overworked and may not be responsive to your request. If you were in department A, the letter should be addressed to Judge Albers, if you were in B then Judge Dekreon. As a tip, if you do the community service via project 20 on the weekends, you will get double credit for your hours.