Well, the quest is about killing the rat but :
- The rat is hidden behind corners.
- The rat has friendly contours and behavior. He will never attack you. So if you don't manually enter combat mode (something that not many player would do by themselves in their own room), you will never know it is there.
- Even if you don't kill it, attack it, or even see it, the room is still yours.
So as long as the dev do nothing to make rat presence more obvious, there will be noobies asking about it once a while.
On the bright side, it also means that we also have authentic new players on AOP, proving their innocence by asking the question. So we know that we aren't playing with the same people forever...