We’re still not understanding each other well enough. Proof of mailing helps, but what you really need is proof of delivery. What matters is proof that that the prosecutor actually RECEIVED the mailing, which is an extra service you must pay when mailing in addition to the certified mail fee. It’s not included. Check this information.
If the court’s copy came back, then you can simply file it with the clerk when you go there. However if the prosecutor has not been properly served then you absolutely MUST do so before proceeding with your case. Don’t argue ANYTHING without discovery. You haven’t even seen the officer’s written testimony. The court will give you a continuance if necessary, but you must ask for it immediately and you can quite possibly do this over the phone without even making the trip. You have a right to discovery.
If you can’t get a continuance by phone, then you should ask the judge for dismissal based on what the prosecutor’s office told you that ”they no longer deal with discovery.” If your dismissal request is denied, then get a continuance from the judge for the purpose of serving discovery. Take along 3 copies of your discovery request. If you only get a continuance rather than a dismissal, then go personally to the prosecutor’s office and serve the discovery request. Have them stamp all 3 copies. Give one to them, take one to the court clerk (or mail it) and keep one for your proof of service.

