How to get a doctors note for financial aid reinstatement?

I am trying to get my financial aid reinstated but i was told that i would need a letter from my doctor to vouch for my medical problems. When i was diagnosed with hypothyroid and hypoglycemia i was diagnosed at the hospital not by a primary doctor, and this was over a year ago, and i have spoken with the hospital and they said they could only give me a statement of the dates which i was in the hospital, they said that if i needed a note or letter i should talk to my primary doctor, but the problem is i did not have a primary doctor then, they recommended a doctor for me to see for a follow up but thats it, and he is no longer working at the same clinic. I have been established as a new patient at another clinic, i have only been there once for lab work to see if my thyroid levels are normal, because i have been feeling really sick lately. so my questions are what would be the best and fastest way to get some type of proof that i have been in and out of the hospital and doctors office that would be acceptable to use in my appeal, and what are my chances of having it reinstated.