2002 X5 Heat Exchanger Loose Clip

[sd02x5]

I have a 2002 X5 (3.0 automatic) that was just in the shop for some work. It needed a new belts and some suspension work. It drove home fine but the next day when my wife parked at home coolant came flowing out. I checked for leaks and it looked like the transmission heat exchanger was loose. I poured some distilled water in the radiator and sure enough it came right out where the heat exchanger connects to the radiator. I thought the clip was missing but when I looked on the other side I could see the black plastic piece of the clip. I reached down, pushed the heat exchanger back on and then pushed the clip in place. A few questions:

1. What are the chances the clip just happened to work it's way loose within 24 hours of having work done in the same general vicinity? I've searched posts and haven't come across anyone mentioning this problem. It also seems fairly easy to inadvertently catch the end of the clip and pull it loose with little effort.

2. Should I have the coolant system flushed and checked now?

3. Should I have the x-rings (2) replaced now?

4. It seems to have popped off just as she was parking and maybe lost about 1/2 gallon of coolant. Any possibility of serious damage?

Thanks.