I recently developed a god-awful rattle in my front right wheel. While rolling (and not braking) on bumpy roads, it sounds like the brake caliper itself is going to come off. When I apply the brakes even slightly, the noise goes away.

I removed the wheel and poked around. It seems that my inside brake pad on the front right is loose enough to rattle around while driving, making that noise in question. The outside pad appears to be firmly in place. I examined the left front wheel and discovered that the inside pad is also loose, but not enough to freely rattle while driving (it has a bit more resistance to movement). I thought maybe a retaining clip had come loose on the right side, allowing the pad to rattle, but the left side doesn't appear to have a clip either, while both outside pads appear to have the appropriate clips.

What am I missing here?