This is could be a fanfic,

loads of years later, they all forgot about it, dipper never solved those mysteries and never got to come back, Mabel had started her own biz and so on. Every night dipper went outside and stared up at the stars

"what could be happening at this minute at places where there is more to what we think?"he was trying to avoid saying Gravity Falls, because he couldn't go back in the following years because something always held him back.

And then, one night, Dipper goes out as usual, and mid thought, he heard it in his head:

"Did you miss me?"