Loose fan broke my radiator? I'm not quite buying it

Audi just diagnosed my car, they say that my fan came loose and put a hole in my radiator. Their quote is over $2000. The service guy had just told me that it's rare for a fan to just come loose but has happened before.
Now, 6 months ago Audi redid my rings and Pistons for the oil consumption problem and when I got it back I complained several times about something seeming to be hot, it smelled hot but my temp gauge was normal but they didn't seem to care.

Being that a fan coming loose on its own is u likely and something seeming hot when I got the car back, is it likely that if Audi had to drop my engine to do the rings and Pistons, that they also had to remove the fan when they did this and missed bolting it back into place?