Hi Steve, I'm not sure what's happened, but they should both be secured to the main chassis tubes by a bolt at their bottom inner-most edge, plus two bolts at the rear bottom edge that secure into the bottom of the panels that make up the footbox. Then, about mid-way up each guard, again on the inner side, is another bolt hole, through which a bolt secures into the front suspension up-rights.
If you can take a wheel off and post a photo it would help to diagnose the problem / pin-point your (missing) screws.