Similar thing happened to a friend of mine, who took her expensive road bike to be tuned for the coming weekend's race. The bike was fine, but having pre-race jitters she just wanted to be certain everything is OK, as several months of costly physical training and preparation was at stake. She took her bike to me that night after picking her bike up from her LBS because of odd noises and mis-shifts. The brakes were messed up something bad and both derailleurs were off by a mile, nothing was even wiped clean. We had no option but to fix it right then and there as her race was the next morning.
I encouraged her to complain, but her confidence had gone and didn't want her bike to be taken back to the same place. I had offered many times to tune her bike for her in the past, but being a good friend she wouldn't have it, and I'm just as pig headed not to charge her for any work I do.
In time she and her husband bought tools and taught themselves to maintain their 4 bikes and they now do their own maintenance. I suppose no amount of explanation or remedial servicing would ever put her mind at ease ever again after something like that, so she found no point in going back.
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