They told you in advance that they were going out of town and taking the dog with them. You still allowed them to watch your dog. They didn't go into your house and steal your dog. YOU let them take your dog out of town. Like it or not, you did. And yeah, things happen that change plans and they won't be back as soon as they thought, but, you let them take your dog with them. That is a fact.
They told us they would be back on Sunday. Three days at most. And their destination was 90 minutes away.