回複：求教Xiaobaitu, I-140 was denied!

Another issue is if you submitted an offer letter, they still can deny you, because you cannot find OBJECT evidence (policy) to prove it.
See this website for some information. You are not alone.

http://www.aau.edu/education/ltr_GonzalezDivine_Denialofpetitions_3306.pdf

The NIW was very difficult at NSC before. Now, it is much more better.

Good luck!