Two things
1. A snake does not have to actually make contact with a heat lamp or che to bet a burn. Think of it like how you get a sunburn.
2. The cage floor directly over the uth should be no hotter than the desired hotspot temp. This should then be covered with a very thin layer of substrate. 1/4 inch or less is about right.
I hope the uth has a tstat. If not you need to unplug and keep it that way until you get a tstat. Google images of burned snakes and you will see pics of burns caused by both uth's and lamps. They are nasty!