Forget dealing with them. Call up BMW NA and tell them that the dealership lost your keys for your car. Explain to them that you understand things happen, but feel they should have done something. They didn't even call you, you show up and "oops, we dunno where your keys are". They didn't offer you a rental and didn't even offer a ride home!
Then again, it's just an e30 :P just kidding! (chances are half those techs would love to buy your car!!!)