In this new timeline of season 4, Walter did go "over there" to get Peter. But the observer never rescued Peter and Walter from falling through the Iceice. This event, the (the falling through the ice,) was the one event starting WaltersWalter's knowledge of the Observers. When, in this new timeline, the observers never had to alter the events, there is no need for the caracterscharacters we know of to know anything about the Observers. Yet...