The classic 1958 SF short story "Or all the seas with oysters", by Avram Davidson, addresses a similar question: why do safety pins always disappear, and why do coat hangers magically appear in closets? There is a copy of the story on the web, apparently scanned using OCR (with some consequent minor errors) and most likely illegally posted, available here as of today, but perhaps not for long.

If the plectrum is the larval or pupal stage, then what larger, nominally inanimate object of a roughly similar form do we often find there to be a surplus of?