This wasn't there when I took a picture of my dog a month ago.
I don't remember seeing this when I took a photo of my dog a month ago.
ーThis wasn't there when I took a picture of my dog a month ago.
「1ヶ月前に犬の写真を撮った時には写ってなかった」
this wasn't there で「これはそこになかった」=「これは写ってなかった」と言えます。
to take a picture of ... で「…の写真を撮る」
a month ago で「1ヶ月前」
ーI don't remember seeing this when I took a photo of my dog a month ago.
「1ヶ月前に犬の写真を撮った時、こんなのを見た記憶がない」
I don't remember seeing ...「…を見た覚えがない・記憶がない」を使っても表現できるかと思います。
ご参考まで!
It didn’t show up in the photo I took a month ago.
・It didn’t show up in the photo I took a month ago.
・There wasn’t anything like this in the picture I took a month ago.
・This spot wasn’t there when I took a picture a month ago.
「1ヶ月前に撮った写真にはこんなの写ってなかった」という表現は、英語では **“It didn’t show up in the photo I took a month ago.”** が自然でよく使われます。
“show up” は「写る」「現れる」という意味で、写真や映像の文脈でとても自然な動詞です。