I know its a strange thought being you want to find the Rube and trade with him but there are times I cant be on the computer all the time but want to stay logged in as I do things online and offline (And getting the browser back to the game window when something major is happening can take too long Thus missing the Rube opportunity) So I started wondering if the Rube could go anywhere or??
So far im pretty sure he cant get to you if your in your home or someone elses....I would think inside the tower is another possibility?? The back alley probably too...I usually park my charachter in his home or that off a friend who will warn me if he goes Offline...So I can still be in the game doing things but dont have to worry about immediatly getting back to the game page...Especially when I am doing one of the magic rocks request or one of my own adventures and need to studdy the wiki or forums while in game.
Can you think of other places the Rube cant get to you?? Maybe the Burecratic Hall Buildings?