“I'll miss you.”
Miss here means to feel sad when someone is absent, rather than fail to catch something. I'll miss you. is a common farewell. Compare I would miss … in A1-04.
A1-60 / CEFR A1 / EPISODE 60
Saying how you feel before parting
SceneIn front of the boarding gate.

WORDS & CONTEXT
Miss here means to feel sad when someone is absent, rather than fail to catch something. I'll miss you. is a common farewell. Compare I would miss … in A1-04.
Message is not only a noun; it is also a verb meaning to send a message. Will you message me? means "Will you send me messages?" Think of you means to have you in my thoughts. Frank promises to look at the stars and think of Tina. The stars connect back to Beyond the stars!, the words from their first meeting in A1-01.
Come back means to return, and when you come back means at the time you return. Here refers to the boarding gate at the airport where they are now. Frank does not end with "goodbye"; he closes with a promise to meet again here when Tina returns.