This observation currently has one ID (Genus Nostoc) but is showing up in a search for iconic_taxa=unknown. I’ve seen a few Genus Nostoc observations showing up in this search. I don’t think the user has opted out of community id.
It’s not a bug, it is expected behaviour. Bacteria are not assigned to an iconic taxa in the species tree, thus they appear in unknown searches.
There’s an open feature request for this here: https://forum.inaturalist.org/t/create-iconic-taxa-for-bacteria-archaea-and-viruses/1464