Originally Posted by
pgoat
i do indeed have the screws, and that's exactly where it broke […] actually the half with the hanger is still attached to the derailleur...however, upon looking at it more closely today and trying to fit the two halves together, i see the screw is gone and so is a decent raisin-sized chunk of metal it was lodged in. Will that make this a much tougher fix, or write the old dropout off as a total loss?
No. As noted elsewhere, the adjuster bolt hole is a common failure point, not just on Trek's dropouts, but all dropouts with such holes. If you decide to weld it back together, the welder can fill the missing area with steel. Don't bother with the adjuster bolts. They're not necessary; only a convenience for quickly centering the wheel in the slot. On dropouts that have started to crack but haven't completely failed, I fill the cracks and the hole with brass and toss the adjuster bolts.
N.B. if you do decide to fix it by welding, you may be able to save a little money if you do the work of filing the weld bead flat on the dropout faces instead of paying the welder or bike shop to do it. Be sure to check the dropout alignment before you put everything back together.