What Happened to Peter and the Knife?

Sonia was watching a German TV show when police went to search Sutcliffe's house the next morning. When they explained to her that Peter was in quite a bit of trouble She paid more attention to the TV than to the cops. The knife missing from the kitchen's butcher block matched the one Peter had tried to hide and for me This brings up an interesting question about Sonia If Peter was taking knives from the kitchen and bringing them back every time he went out Did Sonia ever notice or more importantly if she did notice did she care? Well, I wasn't using them to kill a prostitute tonight. So let him do it.