Glad that you found her. It is easy for chickens to fall or to try to get away from others, and end up getting stuck in between objects inside and out the coop. We had a poor little Polish hen who was always ending up missing, and we would find her stuck somewhere or hiding. I have made sure that no one can get stuck anymore. Each evening, I also do a head count before locking the coop. Fluids with electrolytes are best at first. When fully hydrated, offer small amounts of food at first, as others have suggested. Hopefully, she hasn’t suffered any injuries or other problems. Keep us updated on her progress.