Is it my responsibility as his dad to keep track of where things are put down? No, it isn’t! That is why I keep my stuff in the same place, wallet and keys downstairs and phone and kindle on my night table upstairs. My prescription glasses and work ID live in my car.
Usually when Niko asks that question, he is either asking about his iPad, his Nintendo Switch controller, his drink, his toothbrush, mom, or whatever he was playing with at that moment.
Every time we organize his stuff with his help, somehow, it always gets placed somewhere else. That somewhere else place most often is his dresser or night table. His dresser has 8 drawers and I think only 2 of them have clothes and blankets in them; the rest are filled with stuff. He prefers his clothes hung in the closet along with his socks and underwear.