PBW newbie question about cloak ship

[dreamplace]

Could a cloak ship hide in the sun sector like nebulae and storm, it can't be detect by a level 3 sensor?

If yes, then the cloak ship passing the normal space and my L3 sensor should see it before it enter the sun. I've never check the playback, there's a chance that I missed it?

Someone threaten me that a cloak star destoryer hiding in my system. We are at turn 66 in a low reseach cost game. All of my system lanuched the L3 sensor sat. at around turn 35-40. That's very hard to build a cloak star destoryer before that. I guess it will take at least 1.5 years to built a star destoryer on a large population planet, 150% output and L3 shipyard.
Is there a chance that someone can built it so early?