Or more specifically "all these military air-surveillance radars and satellite-born radars and optical systems never have anything to say PUBLICLY ....".
What those systems actually see, and what their operators actually pass to the civil authorities and when they pass it is something that we, as mere mortals, will never fully know.
Regarding the military air defense radars, I believe that the standard "export version" air defense systems have a surveillance range of 170-200mi. How far off of the Egyptian coast did this event take place? It might have been out of range of the nearest military primary radar...