Dr.Gastor was calling Sans, the two talking about the human Alphys saw on the cameras, while miles away from Snowdin, Flowey was on the kid’s shoulder

Meanwhile at the castle…

Undyne: “We have to tell King Asgore a human has come! We can collect the soul and add it to our collection, and be free!—“

Papyrus: “We can’t! We aren’t risking a human’s life!”

Meanwhile when the two got closer to Snowdin, Flowey would speak

Flowey: “Kid. You know that you’re the only human here, right?”