When a dry cleaner can't find your clothes, it probably means they're in the back somewhere. Though it's possible they were mislaid, what happens most of the time when clothes disappear is that they'll simply tag along in the wrong bag, unnoticed until that customer gets home.
And what does that customer do when she gets home? She puts the clothes in the closet. Sure, dry cleaners will tell you there's a chance that the clothes will turn up, and there is -- sort of. But who's going to remember to return a mystery shirt to the dry cleaner? It's best to make your peace, light a candle for your beloved garment and then try to cheer up with a shopping spree.