Hi terp1974 .....
Unfortunately most insurance plans do not consider single sided hearing loss a disability. My personal opinion is given the ever increasing aging population, with accompanying age-related hearing loss, insurance companies have chosen not to cover regular hearing aids.
rupert is correct that if coded correctly, insurance companies are required to consider bone-anchored devices as prosthetics (since a titanium abutment is implanted in the skull) and therefore are covered claims. However, that involves a surgical procedure, whereas a hearing aid(s) can be used/removed as desired.
My husband is in the process of getting new hearing aids (for age-related hearing loss in both ears). Our insurance will not cover it. However, they did guide us to other companies who offer considerable discounts. It would be worth it to call your insurance and ask about alternative ways to pay for a needed hearing aid.
In the meantime, it never hurts to appeal a decision with any additional documentation you can get from your medical professionals. From my experience with other types of claims, I have been successful with appeals.