Thanks, Lars. Just a follow-up here.
I did contact Apple support. Turns out the app was “hidden” from my purchases. How that happened, I have no idea. It could’ve been an update bug, or accidentally hidden by a family member? For reference, here is the support doc which might help other Cubase iOS users. Hide and unhide music, movies, TV shows, audiobooks, and books - Apple Support
BTW, Apple support was stellar. Took less than 10 seconds to get an advisor on chat, and they “unhid” Cubase iC Pro for me right away (though you can do so by yourself via the support doc steps above).