One thing this article didn't mention: when it came to predictability, NATO aircraft were the polar opposite of Zoltan--they often flew the same routes, at the same times, using the same radio callsigns, day in and day out. This made it very easy for him to predict where an airplane would be. In the case of the F-117, I have heard that the pilot made back-to-back passes over the same target and was shot down on the second pass.
I also heard an apocryphal story about Zoltan: After the war he was "debriefed" (not really an interrogation, since the war was over and he hadn't committed any war crimes, but not exactly a friendly chat, either) in order to learn his tactics. After a while, his interviewers realized that he believed that the NATO forces were so arrogant that they had deliberately tipped their hand to him: he couldn't understand any other plausible reason why they had been so bad at keeping secrets, especially in regards to the movements of their aircraft. When they tried to explain that they had thought they were practicing good security, he refused to believe them and accused them of lying--nobody could be THAT bad at keeping secrets!
There are a few references around to how some of his intelligence network involved people sitting outside (military) airports in Italy and phoning in when F-117's were taking off.
Of course, this type of situation is kind of hard to avoid. Making sure that there's no one within line of sight of the take off path of an airport is kind of hard if it's anywhere close to a populated area.
Of course, as soon as one sortie aborts for a SAM threat, a concerted effort should be put into finding the source (and redoubled if it isn't found but reports keep coming in). You can be as predictable as you like if you really do own the sky.
Important safety tip: the enemy always gets a vote.
If he had the intel to guestimate the location or path of a plane, it's just a matter of time before the thing gets hit.
update: some searching revealed that low-frequency/old radars picked it up and some form of SAM got it. But there were bullet holes in the wing, too. If there was a hostile fighter up, that would work if it could be guided close enough. I've read previously that old/low-freq radars would be more effective as they weren't what was modeled when the thing was built.
The stuff's not magic, although the press and popular literature makes it out as such. Far better to fly things w/o a pilot, as holding missile fragments for hostage doesn't generate much interest.