I had something very similar happen to one of my hens. We had just gotten new ameracauna hens that were rather scrawny. Somehow they found a way to fly out of the pen. It was about March when this happen so there was still a lot of snow on the ground. I went to the coop to find my hen covered in blood, bruised and feathers everywhere! My dog was laying beside the chicken looking pretty guilty. The hen had ice stuck to her feathers and she was almost frozen. We took a blow dryer warmer her up, dried her off and put her in the house in a big dog cage with food, water, a nice bed and a her other hen friend. The cuts and bruises eventually healed with us washing them out with saline solution and then put some ointment on top of it. She also had a small hematoma but 4 months later is fully feathered, totally normal and laying like crazy!