Well, name calling certainly won that argument. Oh, hang on, no it didn't.
Noise that is indistinguishable from white noise is -actually- white noise. If you can't distinguish a signal from noise, then it's not a signal.
If you can distinguish, then you can recognise it as a signal. Even in a signal that looks a helluva lot like white noise contains the traits that allow you discern the difference. Even if they are well hidden, they're still there, which -actually- allows you to distinguish between the signal and nose. The casual observer might walk past such a signal, but we're talking here about an signalling method that will be available to read - anyone who knows what the signal looks like and is looking for such signals will be able to see it, even if they can't decrypt it because they don't have the encryption keys.
The problem here is that you've (rather stupidly) assumed that the poster I replied to may have meant that an encrypted signal could be indistinguishable to the casual observer. But they didn't say that, it was -your- assumption. Fortunately for you, there are some smarter people here to put you right.