Lego's Law is the law of not finding what you need at the moment, finding it en masse when you don't need it and again any particular thing is disappearing should you need it again. I think this "Lego - Effect" is perhaps the same with anything on the world, so let us have a look on the logic and happenings of this curious law, where we will discover and observe the logic (and illlogic at the same time) of quantums and other weird things. I will use Lego as an example through the whole Post, but you could replace Lego, by anything else you like as it is a universal law (maybe even a universal natural law, who knows...).
First, when you look for a particular Lego part, you will not find it. When you think you already touched every part, you have still not found it. There is a particular reason why the quantums of each Lego Brick have that curious behaviour: You didn't touch all parts in the correct order. Only after you had every part in the correct order and the correct time in your hand, will the Lego quantums show sympathy and will reform themeselves to the part you are looking for.
After you finally found that particular part, the quantums start heavily laughing at you. You will recognise that when you suddenly find that one particular part in masses. Over and over again. About 80% of all parts are transforming into that one special part. Alright, when you look for the next part, this whole procedure starts over again. You know that quantums form very fast, uncatchable with a view, and any time one brick is hidden under another, the quantums are starting to transform. Are parts that are hidden under parts really there? Or are they just appearing when you dig them out? In what state is Schrödingers cat? The same question. The only one who may answer it is probably Chuck Norris. So you see that Lego is actually applied quantum physics.
Ok, so when you need that part, for which you have been looking for hours, and finally found out that almost ever part is that part, again (Lego is actually a searching task, not a building task, maybe Google will extend their algorithm to solve Lego's Law - I hope for it) you have no chance to find it again, as all Lego quantums are, once more, transforming themselves to different Lego parts.