After looking up a couple of tutorials for how to disassemble an iPhone I grabbed some tools and went at it.
For those of you who are in this situation and want to fix it, here are the steps:
1. Take of the black rubber piece on the bottom of the back panel (slide some sort of prying tool around the edge where it meets the back cover.)
2. Take out the three small screws (one on the left, one middle left, one right.)
3. Use a razor blade and slide it along the side from the base of the phone to the top and then around. Do this very slowly, and while you are sliding it, gently wiggle it to pry up the back until you hear the clips pop off. Go all the way around the phone until it is loose, and then pull it up from the bottom of phone. BE CAREFUL WHEN REMOVING IT BECAUSE THERE IS A CABLE ATTACHED AT THE TOP OF THE PHONE.
4. Look inside the case where the switches on the side are located. In the upper left corner there is a small spindle, and somewhere floating around should be the little semi-circular piece of metal that actually spins to vibrate the phone. Its this little guy that was rattling around.
5. Gently push the spindle down till it stops, and unscrew the tiny screw holding in the box the spindle comes out of.
6. Position the semi-circular piece of metal in the corner, and navigate it back onto the spindle. You may have to push the box that holds the spindle down a little bit to fit it (thats why we unscrewed it.)
7. Turn on your phone, hit the ring/silent switch and make sure it spins. If it does, snap the case back together, put back in all screws and you are good to go.
I hope this helps somebody, as this seems to be a common iPhone problem but I haven't seen any tutorials on how to do it.
