When did you come home? I didn't even know you were here.
I didn't realize you were here. When did you get back home?
ーWhen did you come home? I didn't even know you were here.
「いつ帰宅したの？帰ってたのすら知らなかった」
to come home で「帰宅する」
ーI didn't realize you were here. When did you get back home?
「家にいるの気がつかなかったよ。いつ帰ってきたの？」
to realize で「気がつく」
to get back home で「家に帰る」
ご参考まで！
いつの間に帰宅してたの は when did you get home とも表現できます。
Get back と表現するのも有です。
やましいことをしてそうな相手に問いだす感じの表現で良ければ
Since when を使うのも良いでしょう。
いつからと言う意味ですが相手の言動を疑問に思う場合に使うのに
おすすめです。
カナダ 
日本 
