h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If you put something in a safe place, somewhere that no-one will be able to find it, you will also never be able to find it.

Unless you employ a small child who will find in it in two minutes.

Your wife will do just as well as a small child, with the added bonus that you will receive a withering look (along the lines of 'what kind of idiot did I marry') when she hands the object over to you.

But don't forget that sometimes you can trick it to come forward
- if you manage to pretend you don't care about the missing object,
but you are really looking for something else!
The problem is that you have to be a really good hiding your basic intention;
things in safe places are extremely good at reading people.
And if it should even suspect you to be looking for it - you bet you will never find it!

The corollary to this is if you remember where you put something, when go go back to get it, someone else will have moved it to 'put it in a safe place'. They will not, of course, have told you this, neither will they be available when you want the object. Mothers (and wives, but not fathers and husbands) are particularly prone to this.

Finally, an explanation as to why when I return to the 'safe place' the 'something' has completely disappeared. Thank you so much.

I've still got to find an explanation as to why, after realising the safe place has lost my keys for example, I turn the house upside down, periodically returning to the 'safe place' and staring at it, convinced the keys will magically reappear there.

Probably because they will. See 'Inanimate Conspiracy' thread.
Also...Dirty habits of common household items:

Thumb tacks – nasty habit of free falling off walls and strategically positioning themselves to injure human feet.

Nail clipper – This always runs away from wherever it is you left it and works in conjunction with your cuticles to devastatingly annoying effects.

Socks – Single socks frequently leave their partners to have affairs with other socks. The abandonee then proceeds to evaporate into nothingness or is discovered five years later in the darkest recesses behind the bicycle in the garage.

Soap – Tends to exhibit a magnetic effect when it comes to hair…

Toilet paper – Competes with the Nail clipper in games of “Haha, you’ll never find me now you bastard” and occasionally smugly sits there in front of you knowing that you’ll never figure out how it got so wet in that one particular spot.

Garden Hose – Tries to communicate with the aforementioned bicycle and frequently strangulates it as an approach to saying “Hi!”

Lawnmower – Tries to stop the garden hose.

VCR – Constantly tells you that it’s pre-set to record something whilst the remote control has left on an expedition to explore new life and civilisation under the couch.

Personal Computer – Dies occasionally.

Microwave – Decides to ‘experiment’ with your food. Moody reactions to different types of dishes resulting in over/under heating of food (delete as applicable). Plastifies Pizza. Makes thoroughly unpleasant sound reminiscent of a small nuclear submarine. Sonar ping included.

Or a mother can find things in an instant. And then they'll either just laugh at you because it's in the stupidest place or they'll give you a similar look saying "is this idiot really my son/daughter?".