My First Overseas Trip not unlocking

[Niilismo]

Is this trophy supposed to pop when you first get to the second island? Because it didn't pop for me, I got to the second island and unlocked Sea! Sea! Sea! and still no Overseas Trip. Is there a more specific action I need to take or is it just glitched?

[Niilismo]

I just got it, I think I know why it didn't pop before. It seems to pop the first time you get on one of those detachable platforms and detach it from the island. I didn't even realize you could do that (you need to zoom out before you get the option to detach the platform and it hadn't occurred to me to try zooming out), so I initially got to the second island by flying there as the balloon while holding hands with the Mayor.

 

Every guide seems to list this trophy as unmissable, but it isn't (unless you're forced to use the platforms later on, I haven't progressed past the second island yet).