Your question poses several questions. (1) Did the condition of the parking lot violate any building codes. Most building codes require that there not be any changes in elevation of more than 1/2 inch in an area where people would be expected to walk. Absent a code violation, you would have a difficult case and be required to show the store knew about the "defective" condition and failed to repair it. (2) Who owned the parking lot and had the responsibility to repair? It could be either...