And, don't forget the "reverse-illusion".
An "illusion" is when you see something that's not there, the "reverse-illusion" is when you know darn-well that something is there, you just can't see it.
Like the screwdriver you know for certain that you just placed on the left side of your workbench, but when you go to pick it up it's just not there. It's usually magically teleported back into the toolbox or somewhere equally unlikely.
No, it's not "age", I've been having this problem since I was an apprentice!!