Many years ago, I was working on my former house to help it sell. We had already moved, but I would live there for a week at a time while working on floors and similar projects, alone. I had enough basic kitchen stuff to cook and eat meals, a mattress and bedding to sleep on, and so forth. I also had all the tools I needed for the projects.
At one point, over the course of two days, I pressure-washed the entire exterior, and then raked the yard. It was autumn and unseasonably cold. My hands were wet and half-numb all through both days. On the second evening, I realized my wedding ring, which had always fit a little loosely, was missing.
I searched for it for another two days, going over every inch of ground looking for where it had slipped off and then possibly got stepped on to press it down into the mud. (The house was surrounded with mud after the pressure-washing.) When that didn't work, I borrowed a metal detector and searched for it that way, including un-bagging all the already bagged leaves I had raked up and spreading them out and going over them with the metal detector, so thoroughly that I did find a small rusty nail and a few pieces of wire. But no ring.
With no choice, I got back to work and eventually completed the move. Eight months later, at our new place, I went to get some gardening tools from a sturdy wooden box we hadn't yet unpacked. Securely and carefully placed in a bottom corner of that box was my long-lost ring.
No, it couldn't have fallen into the box while I was working. The box wasn't outdoors with me then, it was stacked up with other things to be moved on my next round trip. Clearly I had worried about the ring falling off in the cold wet conditions, and had placed it somewhere it couldn't possibly end up left behind. But I had no memory of having done that. It almost makes sense that I didn't remember doing it at the time I found the ring the following summer, but I hadn't even remembered it a day later, or else I wouldn't have gone to extremes to search for the ring in the yard. Even though it had been a sensible and thought-out and somewhat unusual decision to take it off and put it there. Not like putting your keys down in some random place after walking into your home.
I'm not, generally speaking, an absentminded person who often misplaces or forgets things. Yet, that happened. Absolutely true story.
The more interesting question is, what can you do about it? You might consider exercises designed to "train your will" that you can find in books or web sites. Such exercises typically involve doing things that have no value or benefit to you other than that you decided to do them and then really did. A beneficial side effect of this is that it teaches you to pay more attention to your ordinary surroundings and your own routine behaviors. Too many people more or less sleepwalk through their lives. Fourteen is a perfect age to learn to do otherwise.
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Here is a list of 100 suggestions for such actions. Please don't annoy Violet. Or if you do, please don't tell her I sent you there.)