That happened to me on christmas day, I also felt bad about my own neglect. When I locked up it was already dark and was busy preparing the meal so I rushed out there to lock the hens in, didn't have a torch to check if they were all inside and didn't worry about going back out with torch to check, wish I had because typically the day you don't double check is the day one has decided not to go in. Pile of feathers and one missing bird the next morning. Felt terrible about it. We all make mistakes and it's easily done, sorry about your loss though, not very nice is it.