OK, so this definitely is a bug, unlike my last assumption.
Due to pilfering neighbours, I had the 'bright' idea to hide some of my more valuable items in my cotton fields as a stop-gap measure until I could build more adequate defences, as the growth of the cotton obscured them. However, its so obscured that I can no longer pick any of the boxes up. When I try to harvest the cotton in order to reveal the crates, i am also unable to do so as some of the crates lie on the access square for harvesting fields.
Does anyone have any bright ideas?