I'd like to go ahead and submit that the final pill Wrench took from Marjorie's house turns up in the search. He won't have anything to say to the officers in his home and will instead wait for the interrogation by Dick and Norman.

If he asks where he came by the pill, he'll put on his best surprised face and say that he took them because he had a headache and he's already taken a few of them. (He won't immediately say where he got them.) He'll act concerned and ask if that's some kind of problem.