I think this is a bug? I read that this apparently happened to some people with some previous expedition reward ships, but it’s the first I’ve seen it. Steam version.
When I tried to claim the ship, my only claim option was to buy it for 1400 nanites. I hadn’t that much left, I basically spent all my nanites on minotaur AI and upgrades (because fuck having to fight yourself in this game). Since I couldn’t buy, I had a warning I would not be able to claim it later, and even though I cancelled, while I was trying to farm for nanites that game switched to normal save and I couldn’t claim anymore (even from Anomaly).
I’ve confirmed in another save that the reward is available, but since I don’t have that much nanites, I haven’t try claiming yet, just in case it got eaten up again.
If I remember correctly, once I finished the final battle the ship automatically landed nearby, ready to be claimed. I don’t think I even claimed it in the Expedition tab before it happened. I know I wouldn’t have had 1400 nanites.
It’s possible you missed the ship or that the expedition glitched. The bug might have gotten patched in an update but it didn’t matter to you because your game had already converted to Normal. Poking around Reddit, it sounds like others had similar problems claiming the ship.
If it was there and I missed it somehow (doubt it, I spent a while in the area patching up my minotaur etc), there is no reason for the buying interface to even show up. I think that definitely counts as a bug.