The Courtship of Eddie’s Father? The movie not the TV series.
Both have widowed dad of little boy. Little boy seeks wife for dad. Dad not going for boy’s choice. Boy precipitates crisis by disappearing to bring the two together.
Of course in Courtship the two leads know each other, indeed live in the same apt. building.
The only question in my mind is did Nora Ephron do it deliberately, throwing all that Affair to Remember stuff in as a smokescreen (after all, in a sound bite Affair has more name recognition than Courtship) or inadverdently, not realizing the story came from a movie she’d seen a long time ago.