I have three gorgeous Rhode Island Red hens. Every night at dusk like clock work my three hens return to their coop after a full day of free ranging our property. Tonight one of my girls did not return. One of her sisters seemed quite upset. I carried her around the property calling for her sister. I've been checking the top of the coop for hours. She has not returned. They are ten months old and such sweet birds. I saw all three of them at 5pm and by 7pm one was missing. It was still light out at the time I realized she was missing. Any advice? My little boys are so sad as am I!