Very lame of the garage to turn round and say that. Its not like they just fall off! I fitted my pads myself and had no probs at all. Like saying, "Sir, you fitted my break pads last week, and they have fallen out...." Id not be happy with the garage at all!
Best of calling your local branch, think some of them are from the stone age as Ive never had an email response back from them!
anti rattle or anti squeal ? either way its virtually impossible for them to come out i have just finished changing my front discs and the caliper has to be apart for the anti rattle clips to come out and there isn't much room for the anti squeal shims to move either. I think garage man speak with forked tongue