There's a lot in Blade Runner 2049 that simply goes unsaid, meaning that untangling and unpacking some of the plot's details and revelations is going to be a little fuzzy—just like the original. But one thing seems pretty clear by the time the credits roll: Ryan Gosling's character, K, is the decoy Replicant made of Deckard and Rachael's daughter.
We can glean from the clues K follows throughout the story that there is a decoy, and before the big revelation near the end we're meant to think that the decoy was a girl, and was dead. Adding to the potential confusion, the leader of the Replicant rebellion, Freysa, never points her finger at K and says, "you, guy with the weird face—you're definitely the Replicant decoy." Even still, we can piece together just enough information to know who K is, and what role he was always meant to play. K was implanted with Ana's memory of the wooden horse and the orphanage, so if anyone followed the clues to find the missing baby, they'd end up finding K—the boy that was listed as alive.
Of course, as foolproof as the baby-hiding conspirators' plan seemed to be, they didn't count on their decoy actually becoming a detective and tracking down all the clues himself to find…himself. And, well, no one would've known to find that wooden horse at the orphanage if they didn't have that memory implanted…which means that no one would've ever found Deckard…which means that his daughter would've stayed hidden if K had never existed at all…
Man! What a lousy coincidence.