Oh, I am so sorry. That is so terribly hard to handle! Every chicken owner knows what it's like to make a mistake and lose a creature under their care- whether its forgetting to close the gate and night and a raccoon massacre occurs, your dog getting out and killing your birds, or any number of things. It was an honest mistake, and I am sure you'll never make it again- but its hard not to feel bad.
What I do when I make a mistake like that and cost one of my precious birds their life- I rescue something! I look for ads on craigslist or elsewhere for people giving away chickens who don't seem to care what happens to them and I give them a forever home- that way I can at least know that I have saved this chicken from a potentially disastrous life with someone who would have killed it or given it an otherwise sad and unhappy life. Spread the love, save a life in honor of that baby!