trade ship has no assigned home planet

I just got this message in my current game.   My thinking is that this ocurred because the  home planet of this trade ship has migrated to another faction.  So I didnt find out about it until the trade ship arrived at its destination.  (just guesing but it makes sense to me).   I am gaining a lot more than I am losing so its not a concern but I wonder... how do I now assign this ship to a planet?   Just travel to any current core world of mine (or any colony)?  I will try that anyway and report back.  Trade is important to me as I have 20-25 trade routes that constitute about 1/3 of my weeky income.