"The book is in my hands."
Translation:किताब मेरे हाथों में है ।
I don't really understand how that structure changes the focus in English. The less natural, "In my hands is a book" seems to shift the focus & mirrors the Hindi word order of the person's question.
I don't know enough Hindi to each of these English constructions, but the subject and object of the preposition remain the same in each of the English constructions. "There is" vs "the", though, is subtly different in English and does exist in other languages as well (Spanish — hay vs el).
Regardless, should the original question's Hindi construction be an accepted answer (should it be reported as such).
It would essentially mean the same and it should not have been marked as in-correct. Saying "Kitab mere hath'on mein hai", is probably more correct but still "Mere hath'on me kitab hai" is also not wrong.