What is the law regarding unadvertised or undocumented return policies and refunds?

If your deposit money on a motor vehicle is not returned, it can be viewed a couple of ways depending on the existing provisions in your contract and how it would be viewed by a judge if you sued. For example, if you paid a deposit to keep the option open to possibly purchase the vehicle, then the advertiser/seller of the vehicle gave up as his or her consideration taking the car off the market for a certain period of time. If you refuse to purchase the vehicle, then the dealer/seller gets to keep the option money. As to the other way to look at it, if you put a deposit on a vehicle and financed the vehicle with the dealer and it turned out to be a bad car (a lemon), you need to understand that you have two roads, one for used cars and one for new cars. The California laws help protect new car owners with very extensive lemon laws.  However, as to the used car issues, figure out if your dealer is licensed to act as a sales finance company and if so, then complaint to the agency who regulates the dealer (dmv and department of financial institutions). If the company is not licensed to act, then still contact the same agencies.