In the first place, a Use-It-Or-Lose-It vacation policy in California is illegal.
Vacation pay accrues (adds up) as it is earned, and cannot be forfeited, even upon termination of employment, regardless of the reason for the termination.
See also Question 4 here:
http://www.dir.ca.gov/dlse/FAQ_Vacation.htm
And, although I cannot find it at the moment, my recollection is that "discretionary days" or "floating holidays" that can be taken at any time are treated the same as vacation for legal purposes.
The converse would be, for example, if you got your birthday as one of those days, or the company designated specific days, such as the day after Thanksgiving, as one of the floating holidays. In these cases, since the additional time off is restricted by the company, it would be the same as a company holiday, not vested, and therefore not payable at termination. You can call the California Division of Labor Standards Enforcement to confirm, but I think I remember this correctly.