That may have been the case. No worries. Now you know. But ALL heat sources should be regulated by a thermostat. I'm willing to bet my house the previous burn was from an unregulated heat mat.
Heat mats are not for ambient temps, they are designed solely to provide a hot spot, primarily used for digestion. Heat lamps are used for ambient temps. You can definitely get away with not providing belly heat though. I don't run belly heat with any of my pythons or my hognose. But, that means either heating a room in winter or upgrading to a Radiant Heat Panel (by far the best heat source). In winter I heat my snake room and use the RHP to provide a warm and cool side. In summer, my snake room stays low 80s most of the time, so my heating equipment hardly turns on.