There are a few things you can try. First, when you are examining the facet, move the stone so that the light reflection is not directly shining back at you. You can see the scratches when the light is at a slight angle from your eye. The way I do this is to arrange the light so that I can easily get a full reflection and then move the stone ever so slightly so that the reflection is gone. The scratches then become visible.
Another thing that I do which helps me see the stone better is that I either hold a dark surface or my finger behind the stone, so that I do not get a lot of light from behind the stone.
Another thing that I have heard mentioned but that I have not yet tried is to replace your frosted bulb with a clear bulb that has the element exposed. This provides a smaller light reflection.
Tom Mitchell