Xoutpost.com - Problem with dealer service...

My wife owns a '05 BMW X5. Three days ago, I took the x5 for brake service at our local BMW dealership. There was a warning light for a brake lining service. I guess that meant the pads were becoming thin. We had planned a trip to Lake Tahoe for the holiday weekend so I figured it was a good idea to get them replaced for the mountain travel.

Yesterday morning we headed up to Tahoe but half way up the twisty mountain highway, I heard popping sound everytime I depressed the brakes. I wasn't sure what it was at first but after about 5 more minutes of driving, the brakes started to make screaching sound, car was vibrating, brakes were mushy and I was barely able to stop the car. Thank goodness it was an uphill climb. I managed to barely stop without rear ending the car in front of me and pulled over to the side. I had road side assistance tow my car to the nearest BMW dealership which was in Sacramento. Waiting almost 2hrs for a tow truck and with Friday holiday weekend traffic, it was a nightmare of an afternoon with two grumpy kids and a wife. We barely made it to the dealer before they closed and was able to get to Tahoe in a crappy loaner.
This morning, the dealer called me and said there was a bolt missing that held the front left caliper together. He wasn't sure if it popped out or if the first dealer forgot to placed the bolt in. This is so negligent. There was some inner wheel damage but nothing major.
We are so lucky to have this brake fail before we got to the top and drove down through the twisty mountain. I can only imagine what would have happened if I lost the brakes on that descend.
I am sitting here contemplating about this incident. I am turning 40 tomorrow and having this happen has left a sour note on my otherwise a pleasant weekend.
What course of action should I take with this dealer who serviced the brakes? I know no one was hurt but I can't let this pass by quietly.
Sorry for the long story.