The easiest thing to do is to check online. Those tend to post fairly quickly and you can simply pay it and leave the car's owner out of the middle.

California municipal non-criminal violations are not linked to any master database used by CBP, so the failure to pay won't affect your ability to enter the US. But, if you do nothing, the ticket will go to the vehicle owner who will complete an affidavit including your information. That may affect you if you are back in California driving and are ever stopped again.

Don't be "gutted" this is a minor infraction and it does not create a criminal record because it is not any form of a crime.