I have the PC version and have experienced the same with the tractor as I was driving along. I fell through ground into a cave below the surface. I quickly jumped off the tractor and somehow managed to appear at the surface but died. I remembered with the beta versions that you could find missing items and quickly marked the position of where my stuff was. Afterward, I went back to the site and found the stuff that was in my backpack on the surface. Next, I dug down to find the missing tractor and found it in the first cave below the surface.