Every structure has a 30-day deletion timer, whereafter it will be deleted. That’s the reason you lost your ship You didn’t touch your ship since November, so it was deleted four months ago.
As an exception I restored it now, but remember to touch your structures. There’s also a Keep Structures (Holiday) package in https://support.hws.global, or you can ask a friend to touch your ships for you. It doesn’t need to by you.