That's disgusting. Years ago when I used to go down there I never saw anything like that. Never. Once, though, I met a a feller way back in the Plains who flagged me down. His car, a VW Fastback, was buried in deep sand. He said it was just stuck there but when I offered to try to help him get it out he didn't seem to be interested so I figured he was dumping it. I went back to the spot a month or two later and it was still there. Years later I myself got stuck in deep sand in a low slung rental car in a very remote part of the Plains and, after a whole day and a cold night trying to dig myself out I wound up hiking out eight rainy miles to get help. I recently saw an excellent trick to extract yourself from such a situation on an Australian video on Youtube. What you do is tie a branch of wood through the wheel or wheels to give it traction. Don't know if that trick would have worked with that rental car. Also you'd need some rope, and I don't think I even had any with me. In my own vehicle I carry all sorts of emergency gear.
