Accident Damage Car Not Disclosed

Peugeot Fourways in Sandton sold me a Golf 6 GTI in 2012 when the vehicle was a year old and did not disclose that it had been involved in an accident. Now when I decided to trade it in, the current dealership did an HPI report and it came up that it was involved in an accident.(Im losing between 20k to 30k)I contacted the dealer principal and 2 weeks later, no positive response. (Still waiting for directors) I was told that they did not know about it and the problem lies between me and the previous owner. How is it that a so called \Reputable Company"does not do an HPI report on trade ins and still claim to sell \""Clean\"" cars. What guarantee are they giving to potential customers ? I have purchased 2 vehicles from this dealership and they were very prompt in ensuring the sale goes through....but when it comes to complaints"