Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
immĕmŏrātus (inm-), a, um, adj. [in-memoratus], unmentioned, not related (poet.): juvat immemorata ferentem Ingenuis oculisque legi manibusque teneri, not yet related, new, Hor. Ep. 1, 19, 33: nec tu jam metris meis immemoratus eris, unsung, Aus. Parent. 20.