Not sure if this is a bug or part of the game that I am not aware about (as I just bought the game recently).  I had ship vision with one of the TEC AIs and everything was fine; I could see all of his ships.  All of a sudden, his huge armada just disappeared.  I looked everywhere and could not find it.  Suddenly, after 1 minute or so, it reappears around his planet...

So, figured I'd mention it and either get corrected that this is part of the game or realize that it is, indeed, a bug