I'm fortunate most of my land is near to the house, but we have had stuff taken before, my neighbours more so, including a quad bike.
We've lost sheep, so we never any longer keep them in that particular roadside field. The worst was scrap metal thieves taking a large part of a trailer, they must of used a small crane to lift, cheeky bastards.
Point is, thieves will go to great lengths to take stuff, not much can be done, hiding stuff and spreading it out might help, don't things exist that look like large rocks, but are actually secure storage units?