I know that the laws are different in California, there are a lot more cameras in intersections that take your picture if you run a red light.
However, I don't think that you need to freak out this much. You sound like you're a good driver, conscientious and not like typical crazy teenagers.
Honestly, I live in NY and I've done this a few times before and never got ticketed or caught (I didn't do it on purpose by the way). However, there aren't cameras where I live except for in a few intersections downtown.
Still, don't worry. Let it go. You'll know in a while if that light had a camera or not. The penalty probably won't be that bad if you do get caught.
I think that one of my family members drove in California once and ran a red light in Sacramento, but she never got fined. That happened about 3 years ago.