Lost some Lighting/shading materials

When on the rendering set-up for maya, clicked on my desired item but then when I go up to Lighting/Shading > assign new maeterial I expect to have dgs_material up there but it has been taken off the list. Has anyone got any ideas how i can get it back in the list or another way to use dgs_material on my item. If it helps some more (3-4 maybe) have disappeared as well but they were all there about 1 hour ago, any help would be nice.

Many thanks

No worries, managed to sort it out.