Actually the title is what doesn't change, not the page number. I.e. the object manager has a mapping where a given object (article) is in memory (on what page, pun intended). So you have to go through the object manager to resolve the mapping each time you want to interact with the object... or at least that's how we have it implemented in the web viewer ;)
Isn't the borrow checker supposed to prevent these things? I was still holding an immutable reference.