Right, see my reply to jcims but that's not all of matter. One could suppose I'm going senile and perhaps that's true but the fact is that I've been losing stuff like this since before I was a teenager.

I've figured out the problem: my mind is thinking about all sorts of seemingly important stuff all the time but which in fact is mostly garbage, so my subconscious mind handles what my conscious mind consideres as procedural or unimportant. As my conscious and subconscious minds aren't on speaking terms sufficient for my liking I often end up with the problem of lost stuff.

If I consciously tell myself where I've put something then I very rarely forget where it is. The trouble is I don't remind myself to make note often enough.

My own working model is one of complexity building up over time. You can handle it fine as long as you don't have many fields of endeavor, you have plenty of time to periodically focus on them, keep the stuff organized, can fully finish a project and button it up, etc. But then things happen where you're forced to clear out your mental cache, or even screw up your organization/storage system for whatever, and it comes crashing down. Then all the complexity you were managing gets in your way, and the problem snowballs unless you regain some bandwidth and take steps to mitigate the decay.

Right, that makes sense. And my explanation is more complex than I could detail in my comment.

I know I have too many diverse interests—fields of endeavor to quote you—and the older I get the more of them I accumulate. On the one hand having many interests is very useful because it allows me to see and understand common ideas or threads across quite disparate and diverse subjects that otherwise would not have been obvious but the matter of administration becomes a significant problem. Often I've little time to deal with prosaic matters so the mundane is often left to itself (disorder accumulates).

That said, I'm instinctively an orderly and tidy person, as I like to say 'there's a place for everything and everything in its place'. I hate mess and disorder but that doesn't mean that I don't experience it—I do so often for reasons that you mention. However, when entropy/disorder around me reaches a certain 'sensibility' threshold I'm triggered to have an almighty cleanup much to the chagrin of others around who have a more relaxed view of disorder.

Nevertheless, I'm not obsessive about it, sometimes I amaze myself at the level of disorder I'll tolerate. (Reordering things is boring and distracts me from my interests despite the fact that I'm competent and thorough about it. Essentially, the more preoccupied I am with something the higher my toleration for mess and disorder becomes).

Have you ever been diagnosed with ADD/ADHD?

No, I can concentrate on jobs for very long periods, if anything it's the opposite problem. (Although, if you think about it the collateral effects are very similar.)

ADD/ADHD isn’t always that you can’t ignore distractions.

It’s sometimes that you can’t stop focusing on something, even if you want to, or need to for your own health (like drinking water, or getting up and walking around tk stretch).

Hyper focus is the term.

Or you find yourself married and with children, and that final step of regaining some bandwidth becomes structurally impossible to achieve.

It all adds up to what I call the 'overhead of living problem'.