If you go to small claims court, you sue the guy who hit your car, not his insurance company. It will be up to the guy to tender the claim to his insurance company, if his insurance company cares to defend and indemnify him.
I assume that you have damage to your vehicle. Through photographs, at the very least, you should be able to match up the tire of his truck and your door. Put a claim in through your own insurance company and/or go to small claims for the deductible or the claim.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. Laws vary widely from state to state. You should rely only on the advice given to you during a personal consultation by a local attorney who is thoroughly familiar with state laws and the area of practice in which your concern lies.
Since you are in California, you sue the guy himself. His insurance company will have to pay any judgment but under state law you name him in your suit, not his insurance company. You can do this yourself in small claims court which is a fairly inexpensive and a simple way to handle a matter of this nature.