Legal Question in Consumer Law in Missouri

Your question is very broad, and does not specify what type of product was being repaired. Generally there is no requirement that a repair facility contact you before discarding a part of something that they are repairing for you. There may be soem stuutory or agency regulation requirment as to certain types of materials, but generally, there is no need to cal, let alone wite. If, however, they throw away the entire thing they are to repair, without your permission, you may have a common law or statutory claim for your loss.

Good Luck