Well, you can file a motion to compel discovery to the court. The court will likely deny the motion but this would be the next step. They did not claim not to have documents responsive but just claimed that you did not have the right for discovery. Google scholar discovery in cases like yours and note the cases in your motion to compel. You'll have a hearing sometime in respect to the motion .. maybe on your court date. Given that you did not post your state, its impossible to tell. In several states, CA included, a traffic ticket is still adjuicated by the criminal practice rules.
So find the rules for your case in your state and go from there.
Most judges will not allow for discovery unless some technical documents are found that you need an expert to examine ... there may be documents like this in your case.

