I've been going nuts trying to find this one. I even remember a couple of phrases in the story and have tried to use those in a search, but alas, I am but one reader pitted against several hundred stories with a character named Helen.
Are you sure you're properly using the Search facility? For example, in Advanced Search and using the Story Text Search box, I tried finding "pulled at his cock" with Boolean Search in the Find drop down box selected. It returns stories with only that phrase. So if you remember phrases, you should be able to find it that way.
That Boolean Search facility is very powerful. I spent some time with the help file for it and found the time well spent.
ETA: Note that you need to put the search phrase in quotes for only the exact phrase to be used.