YOU SAID:
I went missing when I was one thousand years old
INTO JAPANESE
私が1000歳の時に行方不明になった
BACK INTO ENGLISH
I was missing when I was 1000 years old
INTO JAPANESE
私が1000歳の時に行方不明になった
BACK INTO ENGLISH
I was missing when I was 1000 years old
That didn't even make that much sense in English.