I'm guessing your snake didn't eat because he was burned. I got a snake in the mail that arrived really beat up. He completely healed after a couple months and still didn't take his first meal for 6 months.
Most of my snakes prefer mice over rats, but if you can get them on rats it's much better because you can use bigger ones as they grow. The prey item should be between 5% and 10% of the weight of the snake, never much over 10%. I weigh all my snakes occasionally and put their weight above their tubs so I can weight the rat or mouse and figure out which snake should have it based on weights. Although some big snakes will only take adult mice.