A Lost hen

Last night, when I fed the hens, one of the Maran hens was missing, I had a look round for her, but with the strong wind it was difficult to walk and I hoped she would appear when I fastened the hens up later in the evening. She hadn't but as she had been showing signs of being broody, I thought she had found her self a nest to hatch some eggs. This morning she didn't come for breakfast, but when I did the evening feed tonight, she was huddled in the corner of covered part of the run, very,very dead! She showed no signs of being mauled or attacked by anything, so I'm not sure why she died. Very sad, but part of keeping livestock.