Warranty doesnt want to cover my car

I bought a second hand Audi a4 and on the 4th of may i started hearing a strange noise from the engine. As ive been told before that i should take it to an RMI registered dealer i took it to Bosch service centre in Silverton. One of SA warranties representative was sent to check the car and started saying how the car was worked on before and how some bolts were missing from the camshaft so they cannot cover it. I mean how does a car drive for some time without bolts on the camshaft. The stories kept changing and im just wondering what is the use of having a warranty if it doesnt help you when you need it.