The real question is WHAT DID YOU SIGN, IF ANYTHING? Did the paperwork say anything about non-refundable deposits? If so, you may be screwed. If it didn't, call the Sales Manager or GM back directly and demand your deposit back. You could also call your credit card company and explain the situation and they may be able to biitch-slap your dealer and get your deposit back for you. If you signed something that legally says deposit is non-refundable, you may be at the mercy of the goodwill of the dealer. Either way, I would demand my deposit back. Any attorneys care to chime in? I only got as far as Business Law 101 in college.
Maybe MB Corporate could help you as well as your local Better Business Bureau. You may be able to hang your hat on the fact that they never told you - BUT they will come back and say you should have READ what you signed.
GOOD LUCK AND DON'T TAKE 'NO' FOR AN ANSWER! REMEMBER, EVERYTHING IN LIFE IS NEGOTIABLE. STICK UP FOR YOURSELF!