Objects only exist when observed; when you turn your back, they are gone; when you look again, their existence resumes, they are constructed from your memories, which is exactly why they look exactly as you expect them to (if your memory is flawed as to the exact appearance of an object, you’ll never know because it will be reconstructed exactly as you expect to see it).
The solution to the age-old riddle is a simple one - a tree is unable to make a noise when falling unobserved in the forest because unobserved, it simply ceases to exist.
If you turn your back on an object, then momentarily completely forget it is there, it will not be recreated when you look again, but you will not notice because you have forgotten it ever existed.
If you only momentarily forget it is there, then look again, one of two things will happen; either some subtle cue will jog your memory allowing the object to be recreated in the normal position in time for you to see it, or, noticing an empty space, you will be remember it and the universe will have to quickly find a nearby unobserved space in which to create the apparently missing object. Usually this wil be on the floor.
If there is no suitable nearby unobserved place in which to recreate the object, it will remain inexplicably missing and this is what has happened to me today.
Either that or someone has stolen my fucking webcam.