So you believe the silencer was used then?
Yes and No. Had Jeremy been the killer,and knowing the possibility of blood being within the silencer,it would have only taken him minutes to dismantle it and clean it out before returning it to the cupboard.
If Sheila had tried to use it,or one of them,whichever was the one with damage on it,then because she was already downstairs and before she'd realised it was too cumbersome,very likely put it back,though I wouldn't have said it was the one which was " found ".