I have used 'amissus' for 'lost' to have the same alliteration as in loved-lost. 'Oblivione obruere' is a phrase from Cicero, Brutus 60 (again used for the alliteration), one could also use 'oblivione non traditus' or 'non in oblivione'. Unfortunately you cannot use 'oblitus', as it's a part of the deponent verb system and has active meaning.