Hit ~ outside of any chat box, then type “DI” (without the quotes), look at the structure which was taken, and then find the ID of that same structure. Take note of the ID, and type egs:buyback:id, with id being the number you got from looking at the structure.
Please take note of the structure limits, per playfield, in the Map, and it will show you how many vessels you are allowed to have. Also check out the HWS Global Faction limitations as well.
Most PvE playfields allow 2 Faction, 2 Private vessels.