Forrest Gump might have wondered about that, since losing keys are part of life. Had he been asked about it, he probably would have said keys are lost more often than chocolate.
Forrest Wickman reports that you’ve got plenty of space in your brain and it uses very little energy very efficiently. It stores all kinds of “data”, memories, feelings, facts and so on. Before storing, it has to process the data, as in recording it, deciding where to store it and importantly, deciding in cahoots with other parts of the brain to decide when and what to retrieve.
There may be just be too many places for keys. For right handed men, like the right pocket of the last pair of pants worn. Maybe left in the door after juggling too much when entering. Maybe thrown into trash while holding trash and keys in same hand.
An elder once said, “everything must have a place and everything must be in it’s place.” Further the importance of cleaning and oiling such things as spades and shovels was part of the deal to keep equipment in good working order.
The brain must do those kinds of things for us autonomically although this was overheard in a crowd; “I have to forget something to make room for something new.” Computer hard drives crash, files get corrupted, memory has to be added for the next wave of programs.
Not to be forgotten – the round ones might contain marzipan. Chocolate covered cherries are usually in their own box.