You cannot HACK a landline server which is off the grid. the same goes for the iron man suit...
Did you not understand the part where visions fingertips touched ultron's face and shut him off from connecting to the internet... an physical interface is required... even in real life...
If Ultron can connect
wirelessly through the web and internet and infect starks suit, wouldnt Tony be smart enough to Turn his wireless antenna off in the first place to stop it from happening... Tony Stark is smart like that... I mean you do realize how wireless antennas and signals work right?!!?!
The
ghost drives was mentioned in
Iron Man 1.... When Jarvis asked him did he want to put the information on the company's servers he said no. And the scene where Pepper went to the office of Stane when stark handed her the USB that could decrypt and detect the ghost drives he had...
So it's possible...
They didnt mention it because Ultron had the information he needed when he left. He didnt care about that, he just wanted to destroy the world, and like tony he was obsessed with doing things...