It has been my experience that these contractors are independent from the store. In such a case it is unlikely that Home Depot can be held liable. There should be a contract which lays out the relationship of the contractor.
That said, depending upon specific circumstances, there may be some liability if Home Depot endorses the specific contractor or acts as a general contractor. If addition, if the person is an employee of Home Depot then Home Depot is liable.
Please note that this response is based upon the limited information available in the question. In addition, it is not intended to create an attorney/client relationship and is offered only as general information and not as legal advice.
ANY mistake--probably not. Some mistakes--MAYBE. Read the paperwork you signed for provisions about how disputes are handled and what rights you have.
NOT LEGAL ADVICE. FOR EDUCATION AND INFORMATION ONLY. Mr. Rafter is licensed to practice before the state and federal courts in Virginia. There is no implied or actual attorney-client relationship arising from this education exchange. You should speak with an attorney licensed in your state, to whom you have provided all the facts before you take steps that may impact your legal rights. Mr. Rafter is under no obligation to answer subsequent emails or phone calls related to this matter.