dear, a fire burn in scalp if it's too deep will cause alopecia ( bald patch),wherein the hair roots will be destroyed, which can be treated only by putting in new hairs by hair transplant,.... if it's a very superficial burn, it may not cause hair loss, I don't know Wat depth burn your friend had, and there is no specific bald patch healing medicine that I know of, there is no medicine currently that can grow new hair in a bald patch,it's all advertising gimmicks... we need to evaluate your bald patch,  causes for it, and see if it's really bald, or there are thin dying hairs that can be salvaged,  and then only can decide treatment for you..