Inspection did not show that the Septic tank had no drain field - do we have any recourse?

We bought our home 4 1/2 years ago and had a well and septic inspection at that time. The results came out that everything was good. Yesterday, we realized that we do not have a drain field. The water is just flowing out the pipe down the back hill. The reason we never noticed this before is because the washer used to drain out that way, but we connected it to the septic system because we thought it was how it was supposed to be. We knew that trench was there, but thought we were safe filling it in now that the washer was not empying back there. Unfortunately, when we walked out back yesterday, it was full of water with a nasty brown film floating on it. My husband stuck a hose in the pipe in the septic tank and sure enough the water comes right out in that trench. Can we go back to the inspector or seller on this or are we screwed?? We paid for the inspection, they should have been able to tell there was no drain field or should have made sure the system was up to code. We are so upset right now. We have dogs and children. How gross! Oh - and we have deeded lake access. Nice!! My father in law said this is/was a common practice on lakes. YUCK!