An interesting topic, spontaneous healing. Humans and animals alike have the ability to heal or we never would. But, we are trained to believe that only traditional medicine will heal us. Some external force is required to bring us that healing. Psychologically speaking that is true if we are brought to the belief that only an external force will do the job. Speaking simply.
If you conduct a search for spontaneous healing, you will find lots of references. Many testimonies of God healing in an instant. Different forms of energy healing bringing that sort of cure.
However, it is my belief that no healing can occur unless the person afflicted chooses the belief. If one desires healing, it will occur. How is up to the patient.
Without experiencing spontaneous healing for myself, I cannot offer any evidence. But I can tell you, there are those who believe homeopathy to be a crock, yet when used on my dogs, they heal beautifully. When using Reiki on my ailing snake, she settled into my hands and by the following day showed improvement. In both cases I also used a change in water, added herbs and homeopathy remedies accordingly. They have no belief in medicine, energy healing, or me for that matter. Yet, they heal.
Not sure if this is a help, can only hope. Blessings on your adventure.