I made a 2 X 2 frame covered in hardware cloth and screwed it to the inside of the coop. This is just extra security from creatures that try to get through the screen. It can be unscrewed easily for cleaning and screen repair when necessary.
That is very sad! Your hen might have suffered from a fracture or dislocation. Most likley she is not walking on it because it causes pain. You could have a vet look at it and determine if it can be repaired. That might be just too pricey though. Putting her down would be the humane thing to do...