If I recall correctly nearObjects will only find objects with classes, nearestObjects will detect all objects (with and without classes). To get a list of only objects without classes use the following code (not my invention, I have mooched it for years). Just change the radius as appropriate (10, 20, etc.), but the bigger the radius the more cpu intensive (10 is not much though):
(nearestObjects [player,[], 10]) - ((getPos player) nearObjects 10)
If the scorch marks are classlesss objects, when they are found they will be referred to by their object number and model name, something like: 156372: foo_bar.p3d. In order to extract the object ID for use you need to do some string manipulation.
Edit:
Is there a chance that the scorch mark is actually a texture that appears when the ground object is damaged?