Warning Light On problems of the 2007 BMW X3

I purchased a 2007 BMW X3 on 7/10/14 from a dealer. At the time of purchase the airbag warning light on the dashboard was illuminated. The dealer indicated they tried to fix the issue by replacing the passenger seat sensor mat, the airbag itself and the seatbelt buckle. Nothing they did fixed the issue or cleared the light. The dealer had indicated that this vehicle had an airbag recall associated with it and I would be getting a letter from BMW in August. This letter would allow me to get this issue fixed by a BMW dealer. I called my local BMW dealer, he looked up my VIN and indicated there was no recall associated with my make, model, year and any further evaluation would be at my cost? was it legal for the dealer to sell me the vehicle with this defect? who is now responsible to bear the cost of further investigation? me or the dealer? what recourse do I have?.

The contact owns a 2007 BMW X3. The contact stated that while driving 50 mph, the air bag warning light illuminated. The vehicle was not taken to the dealer for inspection. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 51,000.