It's been like this a looooooooong time. If you select the search by title, it looks only at titles. If you select the message one (which is the default), it ONLY searches the messages, not the titles. I really wish it searched message+title.
I think it might be a relatively quick fix code-wise to get the default to be to search both titles and body text.
You are two of the most powerful women in the permie universe... Is there some ultra-secret forum where you can put this forward to get fixed? I would consider it a bug the way it's working at the moment and r your case in point illustrates it really well. If there isn't a site software development forum where staff like you can post, maybe one could be created? Or better yet, access given to some existing forum where the IT geeks already go to talk about stuff and get their work done. Paul of course will make the final call but I think there's gotta be some way for trusted folks like you guys to get stuff like this on the agenda so it's at least talked about. Maybe in the end they decide not to for some reason, but at least they might say why and you'd know. ???
Title is an indexed field - when you search something, it tries to match your search term with both the title and body text.
In this particular case with silkmoth, it is a singular-plural thing. You can find that thread when you search for "silkmoths", but not for "silkmoth". Apparently, the singular form was not mentioned anywhere in that thread.
Nut.... Normally this should not happen. Our search stuff should be able to capture keywords regardless of grammatical numbers or whatnot. I need to investigate more into this.