You're right. I did find a stock T-Mobile 7392 rom here and it worked just fine. For some reason, it didn't show up easily on a forum search and took multiple pages of Google to find. Here is a link if anyone is interested. Why it isn't stickied in their forum or consolidated with others is beyond me.
[ROM]RUU_Schubert_TMOUS_3.01.531.02_Radio_5.65.09.25a_2 2.45.50.21_Signed - xda-developers