I don't have any info - just support. My aunt and mother are both cancer survivors. My aunt under went chemo - when her hair first came back it was sparse and thin but it began to get thicker and thicker until she had hair thicker than mine! =) It just took time.
I would think that it would work on a scar. My brother and I were watching some procedure on video once about hair transplants. If I remember right, I think that they can "create" a folicle but I'm not sure. You could try emailing a hair transplant office and ask them. They will know and it will save the trouble of having to call around.
God bless and congrats on the new hair - thick or thin!