NTA: They agreed to TAKE CARE of the dog. Not take it out for a walk to the park, forget it even exists because are so deeply focused on their phones and allow it to get lost. That is not taking care of a dog. I get that they have work stuff, I fully do, but how long were they on their phones that they didnt notice Jaxon was gone? Thats the problem to me. If they knew they could be drawn away by work, they should have never let him loose at all and should have just walked him.

Honest mistake? Maybe I dont think it was malicious. But incredibly stupid and irresponsible? Definitely. Your reaction was warranted in my opinion, losing a dog is an emotional thing, especially due to something so silly. If you really want too, you can talk things over and patch things up once you get your dog back. But for now, I wouldnt beat yourself up over anything.