A few things for you to consider: Did you view the last video it recorded? Above video shows how to see it. It will show direction that drone was headed when you lost signal from drone. You said flight log showed it near pivot tower when log ended and you looked along the pivot. I am assuming that pivot was operating as you were flying. Surely you took that into consideration as you were searching in the field as where pivot was when flying and when you were searching are two different places. Do you have a GPS device that gives you your co-ordinates wherever you are? One of those would be of great help in locating the exact position your drone was reporting when last signal was received by controller.
Hope you find it before combine does ! Good luck and post if you find it.