I am searching very hard for a book that stars a "Keshet" in honor of someone named Keshet
I read a book about a boy named Coby who needed a bone transplant and ended up dying. There is a Keshet in the book who is a baalas Tehuva and her mother is in the profession of design. Anybody who could help me identify this book would be greatly appreciated

I think I know the book. I think it is called "The Transplant". 
It's in a shul near me. Hopefully I can go there soon and find it, with author and everything.
Just to make sure - is this the one where the mother or someone was a stolen yemenite baby?

Yes this is the book.