Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
maestĭtĭa (moest-), ae, f. [maestus], a being sad or sorrowful, sadness, sorrow, grief, dejection, melancholy (class.): ex maestitiā, ex hilaritate, ex risu, etc., Cic. Off. 1, 41, 146: totis theatris maestitiam inferre, id. Tusc. 1, 44, 106: esse in maestitiā, id. Phil. 2, 15, 37: maestitiae resistere, id. Or. 43, 148: sapientia est una, quae maestitiam pellat ex animis, id. Fin. 1, 13, 43: illa maestitia est, caruisse anno circensibus uno, Juv. 11, 53.
Of inanim. things, gloom, gloominess, severity: orationis, Cic. Or. 16, 53: frigorum, Col. 7, 3, 11.
moestē, moestĭfĭco, moestĭter, moestĭtia, moestĭtūdo, moesto, moestus, v. maeste, etc.