I've done it, too, Janie. The bird in my profile picture was one of the best birds I ever raised (you can't tell it from that picture, but sadly, I couldn't find a better one). She was never beaten by an Ameraucana, and landed on championship row a couple of times. She also had nice egg color, hard to come by in buffs. During a period of construction/reconstruction that was taking longer than expected due to weather, everyone was confined to one muddy, over crowded pen. Torrential rains made it impossible to keep it dry, much less clean, I worried about the birds getting sick, so I made the fateful decision to turn them out. The next morning I found her headless body. She'd been killed by a hawk. The only bird it touched, of course. I was sick, and still am. Not only was she a great bird but I won't deny I'd grown attached to her - I'd had her 5 years.
Try not to beat yourself up too much, as they say, hindsight's 20/20...