Hi,
Nice to meet you! My name is Randy and I'm an independent advisor.
On Xbox/PC Game Pass, cloud saves are linked to the game itself and only sync when the game is installed and launched. Unlike Steam, there’s no option to directly download your saves from the client. The saves still exist in Microsoft’s cloud, but the system requires the game to access them. Since the title has left Game Pass, you can’t install it without owning it, which is why it seems like buying the game is the only way to retrieve your data.
Kind regards,