I think you mean the F-117 because there is no such thing as F-119 unless you're talking the turbofan. Also F-117 AFAIK do not carry AAMs, guns etc nor does it have external pylons so I'm not sure how it would shoot down anything. If someone fashion an external pylon for the F-117s to carry AIM-9s than for sure AWACS would detect it since the external pylons would not be stealthy.
As to the general statement of your post I do agree that the USAF did use the F-117s in exercises against AWACS and I do remember reading somewhere about the E3s not seeing them on screen.
Since the 1980s there has been a question about the F-19 designation and rumors of a never admitted to fighter, developed by the Lockheed skunk works, that was operational in very limited numbers.
Perhaps that is what they are talking about.
But it has never been taked about, admitted to, or described officially.
Most rumors, and supposed inside "leaks" say it looks like this:
A couple of model companies even made 1/72 scalle models of it in the latter 1980s.