This just now happened to me when I was in the editor. I was editing one of my latest o!mania maps, and hitting Test still didn't prompt a save after doing strictly SB work. It seems you still have to add a note somewhere for it to prompt.
Maybe it was undone in a previous update, I don't know.
Steps are pretty much the same as last time (except this time I realize you can do it on any beatmap you make [whether you just started on it or are about halfway done, finishing touches, whatever])
I guess for now I'll have to actually click the Save button like everyone else :V
osu! version: 20131106.2 (latest)
Maybe it was undone in a previous update, I don't know.
Steps are pretty much the same as last time (except this time I realize you can do it on any beatmap you make [whether you just started on it or are about halfway done, finishing touches, whatever])
I guess for now I'll have to actually click the Save button like everyone else :V
osu! version: 20131106.2 (latest)