Burns were probably all on his upper to lower back, so not noticeable, just surmizing.
That theory could likely be true because she said the following about the painting of his scar: "An unbelievable miracle that I finished out of my memory" In other words, his original scar is no longer recognizable. By the way, as he pointed out in the beginning of the drama, his scar is not considered a flaw (by the right person) as she saw/interpreted it later as an angel.
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By the way, as he pointed out in the beginning of the drama, his scar is not considered a flaw (by the right person) as she saw/interpreted it later as an angel.