It doesn't have to be you, Wolram. Anyone who has access in the house could be having this sort of "spell".
I spent hours searching for some of the things that went missing, only to find them by accident months later. Once I opened the refridgerator to find, to my complete surprise, I'd put a hammer in there. That time, though, it came back to me: I'd been walking past the fridge with the hammer to put it away in the garage, had a sudden urge for a munchie, and set it on the shelf in there while I grabbed the food, then forgot all about it.
Here, again, it was something I was doing on impulse without thinking much about it: I noticed the hammer where I'd last set it down, decided to put it away, and then, equally on impulse, got distracted by food on the way.
The whereabouts of these things all turned out to be pretty much irrational, and I think it was the result of similar starting out with a rational goal, and then getting distracted by something else on the way. The things might be under the seat of someone's car, or they might have taken them away, who knows where or why. I think it must be a bit like sleepwalking: what you're doing probably makes sense to you at the time but you must be in sort of a trance so there's no guarrantee it would make any sense to you later.
The other explanation, of course, is that you may have been visited by a peculiar burglar: someone more interested in the thrill of invading someone elses space than they are in taking valuables. Hence: the envelopes and the shoe as mere "trophies." I suppose such a thing could happen.