Your statement, "I thought there was a enough separation from him and the bottom of the tank." makes me think you were relying on the substrate to protect the snake. Unfortunately no substrate can keep heat loving BP's from a too hot UTH.
If that is what you are doing, then yes your snake is probably burned
Do you have a thermostat for your UTH?
If not, you need to get one before the UTH is plugged back in.
I hope the Vet can help you, and that the burn is not too bad.
Best of luck.
Keep us posted. We are all pulling for your snake.
David