Our inspector missed that our house is plumbed with Polybutylene pipe?

We just bought the house (a foreclosure) in Jan. in Florida. My Dad is a former engineer and for a time attended A/C school (in his 60's) anyway he has replaced nearly all the interior plumbing under sinks in the toilets and various valves. He said our plumbing was strange and some of it he had never seen (bad sign) We were replacing a wall portion where there was a leak behind the washer, and we were replacing our A/C system in the same wall. The A/C technician noticed the pipe in the walls and alerted us. We then saw that all pipes entering the home were grey and there was one exposed under the water heater with PB printed on it. In spite of signing we would only receive what we paid him in case there was an oversight are we able to get more towards re piping? I saw on Answers that someone paid 4500 for a re pipe.We only paid him about 380 for the inspection could we mediate and ask for more? Do we have grounds to sue?..help.