に気がつきましたか

did you notice

→ に
phrase Rare #41,444
did you notice A polite past-tense question asking whether someone noticed or became aware of something. The particle に marks what was noticed.
JA: 窓の外の虹に気がつきましたか。
EN: Did you notice the rainbow outside the window?

いつ時計がないことに気がつきましたか

When did you notice that your watch was missing?

親子走っていたに気がつきましたか

Did you notice the fox parent and its cubs running?

昨夜地震に気がつきましたか

Did you notice the earthquake last night?