If you don't indicate URM status in your PS/DS, nor on the application (some apps do not have an area for race), how do schools know what race you are? Is it on the $12 LSDAS report?
They guess based on a predetermined formula.
The non-obnoxious response: They will not know. Why would you NOT indicate your URM status in your PS or DS, especially if you see a school that doesn't have an area to indicate your racial background?