They got back to me. No missing bits after all, it just wasn't intuitive to me how it is secured. There's a rubber one-sided grommet with a threaded insert that fits into the front of the bracket, into which the screw through the shield tightens. It seemed to me that would mean there was nothing holding onto anything from the back of the bracket. However, what happens is that as you tighten the screw the grommet kind of squishes into a donut so that it can't pop back through. With enough force I think it could still, but maybe that's a feature not a bug.
I'll post pictures and thoughts tomorrow, weather permitting.