The rear wheel came off of my vacuum, there is a bolt in the center of the wheel, but when I tried to screw it back in, there was nothing on the other side to attach to.
There should be a small piece of metal in the shape of a "C" that clips onto the inside portion of the metal shaft that holds the wheel on. If you cannot find it, you can get one at any friendly neighborhood vacuum shop. (Look carefully at the other wheel to see the clip that I'm talking about.)
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vacuum cleaners.