I am pretty sure the Sewage SCA.B was removed from the game since the Shroom and Doom update? The grate is still covered up with a rock and I no longer get the notification on my locator. However, I still get the notification for the raw science and I can hear it vibrating/pulsating when I stand over its location. A buddy of mine who had the Sewage SCA.B said it was removed from his inventory after the update. Does that make the full SCA.B list at 39 or did they add one to the game (replacing Sewage) making it still an even 40?
I am having the exact same problem. There is a boulder over the grate location and the SCA.B locator still picks it up in this area. No way in the sewer grate however. Also, a lot of the bugs in that area seems to be spawning in one of the rocks. It sounds like a jungle but aphids, ladybugs and ants are all stuck in one rock.