Oh my goodness! This is unacceptable and so tragic! I had a similar situation 20 years ago with our first golden, Carmen.
She had cancer in her snout and lived about 6 months after the diagnosis. When we decided that she had had enough, we needed to let her go and the vet's office "forgot" to have her picked up in a timely manner and they kept her in a freezer for several days. I was so upset and was I was livid! They finally got in contact with the cremation people and got it worked out and within a week we got her ashes. But I do remember the anguish and upset that caused and so I can certainly understand your anger. It is something that will stay with you, but regardless, you did what is right for Jaxon, and he is now running free! I absolutely believe in the rainbow bridge, and know that doggy heaven is where all four of my goldens are running around together. It brings me some peace.
When the day comes that you can talk about him and laugh, you may be able to bring new golden love into your life. We've had to do that so many times in the past 20+ years. It never goes away, but a new love helps. Our Jackson is our current big guy, and I hope we have him for many many years to come. He's not quite 17 months old, and will be a big brother in 2 more weeks when we travel to Wisconsin to pick up our new little puppy. And yes, we know that one day we will need to face the pain of loosing them but they give so much to our lives that it's (almost!) worth the pain.
Best wishes to you!