This happens to me every time I book a flight to the US - my API information disappears no matter how often I enter it, even once I get the green tick in MMB. I have spoken to BA about this a few times but no one seems to know how to resolve it. That said, I haven't had any problems entering the US and my TSA Pre-check / Global Entry still works fine. It's a (rather annoying) mystery... If you find a way to stop it in future, please do share!