I remember commenting on this before, it's been this way for a long time and I've never seen an explanation as to why it works this way.

That specific game you linked to does show up in the quick results that pop up as you type the words into the search field, it only doesn't show when you press enter and go through to the 'full' results.

引用自 sumwun：

When I just search "touhou" and press enter, this game does not show up in the results, even though its title contains the word "touhou" and 2 of its sequels show up just fine. Is there a reason why this happens and do similar things happen to other games?

Because, for some reason the developer has asked Valve for it not to show up in the store search, Bethesda did the same thing with the Original version of Skyrim.

https://psteamproxy.yuanyoumao.com/app/72850/The_Elder_Scrolls_V_Skyrim/

The store page is still there but only the never versions show up in the search.

引用自 MancSoulja：

引用自 sumwun：

When I just search "touhou" and press enter, this game does not show up in the results, even though its title contains the word "touhou" and 2 of its sequels show up just fine. Is there a reason why this happens and do similar things happen to other games?

Because, for some reason the developer has asked Valve for it not to show up in the store search, Bethesda did the same thing with the Original version of Skyrim.

https://psteamproxy.yuanyoumao.com/app/72850/The_Elder_Scrolls_V_Skyrim/

The store page is still there but only the never versions show up in the search.

I doubt this is the reason. The Touhou game still appears as an autocomplete suggestion in the search bar, and there's no notice on the store page saying it's unlisted.