YOU WIN, I've had two jobs like this but not that bad, I just went in and said, OK do what you can and get out, there were just paths, so I cleaned what I could, and what's funny, is that the carpet came out really clean. In both houses the customer never got up from their chairs to inspect, just said thank you.
I hope you were able to bill whoever was paying for this job for the cost of your pads.
I have a Sec. 8 family as tenants in a townhouse condo I own, and they are amazingly neat and clean. Previously, people to whom I am related lived there, and they left the place a mess.