I have a Fuel EX7 and the exact same thing happened to me. Worst part is I was about 6 miles from the trailhead in the middle of the desert. That was a nice long walk back!
My Trek dealer snapped a picture, sent it into Trek, and got me a new chain stay on within a week.
My Trek dealer snapped a picture, sent it into Trek, and got me a new chain stay on within a week.