 Who did you contract with? Who did you pay the money to? Your contract was probably with Home Depot and they would be liable in that instance. Your contract will have their name at the top, signed by their salesman or representative. That's where you should look for indemnity. If the sub says they're only responsible for 00%, file a claim against HD in small claims court and subpoena the sub as a witness to that effect. Or name them as co-defendants and let they and HD cut one another's throat in court. 