That bolt DOES NOT go into the rack-eyelet on the dropout. You're missing a D-shaped nut that slides into the dropout slot. That bolt+ D-nut holds the hanger in place when you unbolt the wheel. Here's a picture:

http://www.bikeparts.com/pimage/BPC109497.jpg


You can see the outline of the D-shaped nut behind the hanger. Notice that the angle of the slot in the hanger should exactly overlay and match the angle of the slot in the drop-out.