I think it depends on what it is the title for. It's difficult to answer if it is "correct or usable"...it's not a phrase that actually exists and is widely known, so it isn't "correct" in that sense. However, this would be an example of creating a new phrase. New phrases are created all the time in English, and are certainly widely used as titles for songs, poems, essays, books, etc. If I heard or read the title "The Slipped Poem" I would be intrigued, and might well want to find out what it means (because the meaning is not immediately obvious), and if you explained the title in some way in whatever you are creating, then yes it would be fine.

Couple of suggestions. - The Tantalizing Poem (suggests you're on the verge of remembering it but can't quite make the final grab) - The Poem That Just Won't Come To Me (means you really want to remember it back but can't)