My understanding is that the LBS just submits the S/N and info to Trek and they send a fork. The error is on the Trek side I believe.
I used to get numb hands with my old mountain bike. My DS 8.5 has the Satellite Elite grips which I think I read somewhere the shape of is supposed to reduce the problem of tingly hands. I'm about 5'9" with a 17.5" frame and I actually got a shorter stem because I felt stretched reaching for the bars.