I tidy his tools away into completely miscellaneous places. He has a LOT of tools.
He'll then ask me where I put his smaller weasel-toothed snoopling spanner, the one which he deliberately left on the bedroom floor a week ago SO HE COULD FIND IT WHEN HE NEEDS IT, and he needs it URGENTLY, so why is it not where he left it?
Sometimes I deny having removed anything from the bedroom floor and accuse him of having lost it himself. Usually I do believe myself when I say this, but sometimes later a vague memory bubbles to the surface and I realise maybe I did move it after all. But obviously I'm not going to back down at that point, having spent 20 minutes vehemently maintaining that I never moved it. I know that if I change my story at a late stage, I will invariably be held responsible every single time he loses any tool in future. So I stick to my story. (If I do manage to figure out where I put the spanner, I quietly smuggle it back into the bedroom and "find" it there "just where you left it".)
Usually though, I truly have no idea whether I moved it and if so where. First we have to play Twenty Questions so I can learn exactly what a smaller weasel-toothed snoopling spanner looks like, in case that may help me remember whether I've seen it. Since DH is singularly bad at describing things which to him are obvious, this takes a while. "You must know the one I mean. It's just like my bigger weasel-toothed snoopling spanner, but smaller." I am not trying to be dense, but I'm sure it seems that way.
I know full well that even when I know exactly what a smaller weasel-toothed snoopling spanner looks like, I will still have no idea where I put it, so this is a pointless exercise. But I go through the motions so as to give the appearance of wanting to help him find it.