I'm SO sorry to be reading this
If you paid by credit card, you are likely safe. If they do not refund the money, dispute the charge and you'll likely win. I'm with BM here on the court thing, i likely would not sue in a case like this as suing takes a long time and will not help in the healing process imo.
I think some type of dedication (tree, plant, or anything personal in your dog's honour) is a wonderful idea.
again so sorry you had to go through this, please accept my condolences.
Sincerely - Marko