Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
immĕmŏrĭa (inm-), ae, f. [in-memoria], unmindfulness, forgetfulness (= oblivio; post-class.): cum reversus locum thesauri immemoriā non repeteret, Dig. 41, 2, 44.