Maybe I'm slow to realise this. but somebody just pointed out in another thread that the Rube can only trade with you if its something in a main slot, not in one of your bags.
Therefore perhaps the reason I haven't seen the Rube in such an age is because I have a bag/pouch/toolbox in everyone of my pouches!?
@ Jasbo - cheers, you may hacve solved a mystery for me :)