Why can't I remove specific Map Revealers on my map?Patch 1.05 for Brood War and StarCraft will allow you to remove all map revealers on a map, but not individual revealers within a location. Invisible or hidden units are not technically findable by trigger, just as you cannot find units in a transport, which are also marked as hidden. This means that you are still not be able to remove any Map Revealers from a specific location, since that would require the game to find them within those specific coordinates, which it cannot. If you need to remove specific revealers, the way to do it is to remove them all and then recreate those that should remain.
http://www.battle.net/scc/faq/trouble.shtml That is to say, you can't use 'remove units at location' with map revealers, though you can use 'remove [all] units'.