My daughter has Reverse House-Elf Syndrome.
It seems to be painless and from what I can tell, actually induces a sense of euphoria in it's victims. It is much more difficult for the parent than the child.
I first noticed it coming on about a month or so ago.
Now it is in full force.
I vacuum, only to put the vacuum away and find that in those 5 seconds, the living room is now mysteriously covered in popcorn.
I begin to load the dishwasher, to look over and find in the blink of an eye all of the silverware has been removed from the utensil basket and strewn across the living room in a pattern that at times oddly resembles crop circles.
I pick up dirty clothes, put them in the hamper and walk away only to return and find that the clothes have left the hamper and are now back on the floor, only now they are in multiple rooms instead of one.
I do an entire load of laundry to find a very questionable shriveled old avocado in the bottom of the washer as I am putting the wash into the dryer... not to mention a Q-Tip, a little car and a small cardboard book.... I'm really not sure how the washer was even open long enough to "collect" said items, but as previously noted, children with Reverse House-Elf Syndrome tend to move at light-speed.
The strangest part of this mysterious syndrome is that is causes the victim to move items from the kitchen into the bathroom, from the bathroom into the bedroom and from the bedroom into the living room and this strange need to move items seems to overpower all other basic human needs.
I've also noticed that it causes it's victim to want to "un-do" things that they witness being "done." For instance, if you fluff and place your pillows on your couch just so, a person with Reverse House-Elf Syndrome will have a compulsive need (after witnessing your hard work) to come behind you and remove those pillows onto the ground and de-fluff them in a series of very creative ways.
It seems that there is really no cure for this syndrome. The best thing you can do is stay patient and stay on top of said culprit, reinforcing the rules until the syndrome eventually (hopefully) goes away. I find that laughter is the best medicine in this case, because it really is quite funny... especially when you search and search and search for your daughters shoes (which have mysteriously disappeared sight unseen -- like many other items in the house), without any luck, to find later that she had actually put them in her shelf where they go with the rest of her shoes and that was the one place you didn't think necessary to look.