> You're not going to get the money back.
Indeed, that's my read too, but he shouldn't just shrug his shoulders and give up.
An option: Call them up, tell them you're short on cash and really need the money, and offer to take 1/4th of the salary you're owed if they can pay you shortly and it'd be a huge favor to you and you'd appreciate it.
This removes the small chance of getting the full amount, but it gives the very-important closure and gets the pay off the top idea on your mind - http://www.paulgraham.com/top.html
The cost to thinking about bullshit like this isn't considered enough. Offer to take two weeks pay and sign away the rest. Then be very, very grateful about it, thank them and say it's a big favor to you and you're rooting for them. You lose the small chance of getting full pay, but you get something and can move on with your life and devote your mental energy to other things.
Edit: The other nice thing about this route is that after going through that process, you're no longer a creditor to them and can call them up more freely without them tensing up and feeling the pressure. Depending on how valuable the contact/reference is for you, that could be better than going more hostile. If you did want to go hostile, small claims court might be a better bet than the wage board, depending on what the cap is in California. Small claims doesn't require a lawyer and is pretty straightforward to navigate on your own.