Disappointed SMD client

I purchased a vehicle from SMD, Blackheath on the 17th of April this year. I had the engine replaced and went for the engine clearance,only for the authorities to ask me where the vin number is engraved on the vehicle as they couldn't locate it. I called SMD head office and they told me I would have to go to the branch where I purchased the car for investigation. When I got there,the unhelpful front desk assistant told me laughingly that she's not sure if it's something they could assist with. By further prompting,they told us that the vin number is located by the shocks of the car, which we have yet to see or locate ourselves. Does SMD not take their vehicles for clearance before selling them? Why could they not actually show us where the vin number is located?