Yes, even if all leaves die, there is still a chance that the plant starts growing new ones from the dormant buds. It is also possible that the rootstock (i.e., herbaceous peony) will start growing. Let's wait and see what will happen.
I know how you feel. Earlier today I went to the garden and found my native orchids shredded. There were four shoots yesterday, and now, there is only one tiny shoot left. As of yesterday, I was thinking that I should protect the new shoots from raccoons and squirrels, but it was raining and I did't do anything. The worst of all, I think that my cat did it this time. I feel horrible and I am very sorry, but there is nothing that I can do now.