Dishonesty and shifting the blame

I recently bought used car at their garage. Only to get home I realize there was a problem with the left mirror functioning. I went back to the salesman who was assisting with my purchase he told me there was nothing he can do since I signed that the car is fine, I only realized that there was a fault at the mirror weeks later after buying, the car is still within the 6 months warranty that I was told about. Clearly this was a **** since I have to cough out money from my own pocket to fix the mirror. I'll be telling people about this garage and I'll never recommend it to anyone.