I checked the obvious place. I emptied the little cupboard out in the end, and checked everything to make sure I wasn't missing it.
So, I went to the next obvious place. And while I was there, I thought it could all do with sorting out. And then it snowballed.
I had stuff everywhere. Piles of stuff. All the little electricky bits, I put into ziplock bags and printed labels for the bags (most of the actual items were already labelled, from a previous tidy up). I took the opportunty to clear out some stuff relating to an old job, and stacked the papers up, ready to burn. This gave me a free slot, so I did some reorganising of that unit while I was at it.
I've managed to clear out several cupboards. I didn't find the charger but, part way through, I remembered recording my embroidery machine, and I could vaguely picture it sitting on the side upstairs.
I did look, while I was taking some stuff upstairs to out away, and it wasn't where I pictured, but the spare battery was.
I carried on sorting out downstairs. I vaguely remembered it had been plugged in the landing, and I'd unplugged it for some reason... and I'd put it in a stupid place. By the time I'd nearly finished the excavations downstairs, I had a pretty good idea where it was. I went upstairs to look - and found it.
I'm actually quite pleased that I misplaced it, as I wouldn't have done all this decluttering otherwise.