What a horrible story :/ I'm so sorry this happened to you!! I had a bird go on a "vacation" if you would like to call it that. I think she was milling around in the neighborhood near me and got caught it someone garage and they closed the door. So she had a sleep over. Or she may have gotten lost and went there because she taught it was safe. Because that's where she lived when she was younger (the coop wasn't ready until 5 months) she did not come back till noon-ish the next day. So MABYE they got locked out. And wandered off. Found somewhere warm and is staying there. And will mabye come back? It's possible.but we had a fox take one bird one night and there was absolutely ZERO sign other than a missing bird and birds going back to the garage, (where they were raised) instead of their coop. They did this the next night at dusk. And wouldn't you know it that two other chickens went missing. So locked up for a couple weeks the birds went. The only sign we saw was the second night, there was some blood on the porch where the chickens were. I suppose they got some on their feet from the other bird. It's a scary thing. And those terrible pet sitters didn't help!!! I couldn't understand if they did everything they could do, and followed their instructions. But you caught them in lies. That's just terrible. And you will never know. I'm sorry :/ hopefully they turn up!