It's my understanding that if you're an LLC in CA you have a Corp number. If you don't have a Corp #, you're not an LLC in CA. 

When you file your LLC paperwork with FTB, they assign you a number.

If you didn't file your paperwork with FTB, you're not an LLC.

So, like Just-Lisa-Now says, check the California Registry. I think you can download a copy of your registration from there, though I don't do a lot of CA business, so I'm not positive.