Doesn't plug anything.
Plugs why they didn't go back straight away. That's something.
Still doesn't explain how they missed the huge obviously alien spaceship within driving distance of the colony.
They hadn't driven to that place yet.
Film never sets up how the planet was mapped out or how frequently colonists traveled out, or how far they went if they did. It also never establishes how long the air's been breathable and conducive to mum and pop teams driving around on their own. It's not much of a plot hole when there's nothing in the film saying "Man, this should've been really obvious!"
It's a weird, jutting shape on a planet of weird, jutting shapes. Eh.