YOU SAID:

The details certainly remained to be filled in

INTO JAPANESE

詳細は確かに記入されたままでした

BACK INTO ENGLISH

Details were certainly left filled

INTO JAPANESE

詳細は確かに埋められたままでした

BACK INTO ENGLISH

The details certainly remained buried

INTO JAPANESE

詳細は確かに埋もれていた

BACK INTO ENGLISH

The details were certainly buried

INTO JAPANESE

詳細は確かに埋もれていた

BACK INTO ENGLISH

The details were certainly buried