Thanks to some sleuthing from @ceiseman who has been going through many observations added to the project, and @harsiparker, the mysterious case of the mysterious case has been solved.

It had been observed by several users in North America and assumed to belong to Arthropoda, but it was, in fact, a geranium seed and its dispersal mechanism (a filament trailing from it).
Here it is:

https://www.inaturalist.org/observations/68020364

Staying with us is an observation from Ukraine (by @dinasafina) of Polistes dominula building a nest inside a chunk of animal bone:
https://www.inaturalist.org/observations/54959613

Happy observing!