Don't see why Jeremy would clean the moderator. He would not notice small amounts of blood on and in a small dark item in dark rooms.
It may have been a spur of the moment decision to remove the silencer after shooting Sheila. After realising the rifle with moderator was too long. So he would not have had a pre arranged plan with it.
He put it away, almost hidden. Not expecting the police to look at it. They didn't.