Hint: any time your insurance denies something, question them. Ask to appeal the decision. Keep calling, they have hidden offices all over the country in many cases. I once spent a whole day talking to United Healthcare representatives - in Dallas, St. Louis, New York and finally California. Ask sincerely, whine, rant, cry, whatever. I made enough of a stir that each person kept kicking me up one level just to get rid of me, and I finally got to someone with the authority to override the decision and fix my problem. I work for the county, and they're "self-insured," so the insurance company just approves or disapproves the spending of my employer's money. My next step was going to be to go to the weekly county commissioner's meeting and speak to them publicly, in front of the TV cameras. I figured they wouldn't be happy to be portrayed as employers who deny their staff needed health care.
Your doctor will advocate for you. He will send a letter or two. He will not take a whole day to make these people uncomfortable, and he doesn't have direct access to decision-makers either. The sad truth is that your treatment was most likely denied by some high-school graduate with a computer program in front of him or her and no medical knowledge. The rules are made to keep their payouts low, so you have to advocate for yourself strongly. And be creative.