Optional Sidequests

Silver Soldier is the Daughter mission. The crashed ship is a wreck north of Nayla, the town before Aiedo and after getting Rika.

I don't think I've ever seen it before! lol. I'm gonna hafta check. And someone somehow deleted all memory on my PS4, it won't let me go into the sound test. Which means that it thinks I haven't beaten the game?

The crashed ship is indeed between Nalya and Aiedo. Look for a huge crater with something in the middle and just walk into the something.

SPOILER (select text to read):

The ship is actually a crashed world ship that escaped Palma thousand years ago, which got trapped in Motavia's orbit. Eventually systems failed and everyone died and over time the ship lost the ability to stay in orbit and crashed. Rika will be able to activate the computer and the party gets information about Palma's destruction and the escape of the world ships.