I bought Zhonya's Hourglass today, but I unfortunately did not remember if I had my Heartseeker's fully stacked, so I wanted to undo it and look, but I couldn't and that could affect stats I was playing with, which is important. I did not move an inch between those actions, so I did not left the base. I played Azir, if that helps with solving the problem.
TTK Dreadnought1 votesi assume you mean seeker's armguard? 
?
The bonuses from 's passive disappear upon upgrading it to 
. However, the stats on are already higher than a fully stacked and 
combined so no stats are lost.
An Undead brat1 votesOh, why the hell was I thinking that 's passive gives the bonus armor when upgrading it? xD And Zhonya's recipe is now 
instead of by the way xD
Anyway, the bug still persists, I could have wanted to decide to buy something else instead of finishing Zhonya and that would still affect my game.