Hey, I'm a little new to reddit so I'm not super great at how this whole messaging thing works, but I've been in the exact same boat and if you need to talk about it give me a shout.
My husband and I tried to adopt a dog last year that we found through a friend of a friend. I had just lost my childhood dog a month before, who had to be put to sleep due to a genetic condition that took him from us too soon. I felt the best way to honour him was to give another dog the good life and care that I had given to him. The rescue rushed our application because we had already met the dog and on paper and in person we were the perfect home for her. We loved her very dearly.
They dropped her off for a trial 2 weeks with us. We had her for 6 hours and took her on a walk, and she was perfect. She had unfortunately had a really rough life, and she wasn't so much afraid of people as they were just alien to her due to the isolation she had experienced in her earlier years. She was, in a sense, 'wild' and untamed.
After taking her for a walk, my husband went inside because she hadn't had the chance to go potty since arriving and men intimidated her more than women. While I was walking her back into the house, she slipped her collar and ran. My husband tailed her for several miles on foot, we had search crews out from the rescue, her foster family with their dogs who she knew, and many kind strangers.
Unfortunately, we received a call from a good samaritan who had seen my husband running and took off with some meat in her car to try to just follow the dog. She saw our dog get hit by a car, and she went to the emergency animal hospital and stayed there, begging them to keep her alive because people who loved her were looking for her. Unfortunately, the dog had to be put down, and the woman stayed with our dog as she went to sleep. She found a way to call us later that night to let us know that the dog had died. We still don't know her name, and wish we knew who she was.
I and my husband blamed ourselves deeply for what happened, especially my husband as it was his first dog. I think what's really important to realize is that you were and are the best dog owner there could be. Why? Because you took a dog who was on the street, and then in a shelter, into your home and you gave her the greatest love that you could. As an owner, that's the greatest thing you can give a dog, and for a rescue dog a new start and a new life is such a significant thing.
I personally feel that dogs aren't simple creatures that 'forget' the bad things. They remember, and there are some cases of abuse and situations that I really feel change a dog forever. She was in a new place, she had lived on the street where running where she wanted was normal. Rescues take years to recover, which is why I have respect for every single person who rescues, just like I have respect for you for taking her into your home and giving her love for the short time you were able to.
At the end of the day, don't blame yourself. You can't lock a dog in a cage to protect it from the world, it has to have a life, and there was nothing wrong with your dog being loose in the house where it was safe. It's a sad, sad thing when their lives end too soon, the dog we lost was 4. But be happy in knowing that instead of being out in the cold on the street, she had known a warm home with people who cared for her in the last days of her life.
I still keep in contact with my dog's foster family, and when I got my puppy, they celebrated for me and they love him to pieces. He has done our hearts a world of good, even if at 6 months old he has no idea how much significance his entrance into our lives had. Don't give up on dogs, and don't ever think you can't be a great dog owner because of what happened.
If you have to be angry, or to have someone to blame, blame the people who put her in that position, blame the people who left a sweetheart like that out on the street with 8 puppies. But don't blame yourself, and be kind to yourself and your family.