SO when talk about this topic, i always have a lot to say...
i am a forgetful guy and put things in some strange places, for example i put my book in my drawer for clothes, so no matter how hard i will never find my book in my book shelf or backpeck.
how to deal with this problem?
every time you lost something, and you found it, like before, it ended and you came back to your normal life. then you lost it again(here "lost" means you forget where you put something), you still had to cost a lot of time in looking for your stuff. But now everything will change by my opinion, i think the behavior, you put something in somewhere you could't remember, is a subsciousness, and samply speaking it calls habbits. we could use the statistic method to work out this kind of prob, i mean everytime after you finding the stuff you lost, what you do is just take a pen and a booklet to write down where you find it, every month(the interval time depends on the frequency of losing things)you should make a breif sumerization, every 3 month you should make a media one, and when it come to a year you will see the annual top places where you put things and then you forget... and you can put it on internet and be illustrated with some pictures.