Yet another classic case to be questioned. What is to say that everything continues to exist when we're not around it? If it's all a figment of your imagination you're creating and destroying the world within your mind every second of every day. Other times you open a cupboard and you know something is right there, and yet you look for it and you can't seem to see it, you'll put your hand right through it spend minutes looking and can't find it then someone else grabs it and it's like it materializes out of thin air, you know for a fact you were just starting right at it and it simply wasn't there, then it was simply willed into existence by yourself or someone else. Other times something shape shifts or becomes significantly different and yet it's like it's always been that way. Things simply may not continue to exist outside of constant proximal attention and when they come back into existence they may be slightly different than before.
Change Blindness is an idea that is vaguely related. I exploits your mental focus on something so that you don't notice things that are going on right in front of you. The invisible gorilla was such an example. The viewer is entirely focused on something so much that they don't even notice a man in a gorilla suit walking across the screen. Sometimes that's what happens is you're so focused on an idea that you probably couldn't see much of anything. You could recognize objects in primitive forms but when you move the bag of salt you don't know what you're moving, or a bottle of ketchup, various cans as you traverse your cupboard you have no idea what you're touching in your pursuit because you're looking into your mind and not through your regular eyes but a kind of ESP. Mastering this view can dramatically change the way in which you see the world. The idea is to never explicitly focus absolutely ever last drop of your attention into anything accidentally or you'll likely miss the gorilla.