Haven't built that kit but are you referring to a weld seam in that area that you lost because of the sanding? If so, I've heard of people using a slow spinning drill bit or similar tool to recreate the look but would recommend trying it out on spare plastic first to see if it's what you want.
DISCLAIMER: I've never used this particular method and am not responsible for any damage done to your kit, powertools, work area, or any other property you may have in proximity to the area if/when you attempt this method.