Runaway Throne Walkthrough
Linzi will come to your throne room and will notice, well, that there is no throne. Go out to the town square and talk with two merchants (Verdel and Hasuff in the center). Then head to the tavern and chat with Elina about the stolen items. The fourth person to talk to is the captain of the guard. Look for him to the right of the throne room entrance. If the captain does not want to talk about the throne (no such dialogue line), then this is a bug — wait for a patch.
After all four conversations, you can only wait for the throne to appear on sale. It will happen after you complete The Path of the Dreams quest and visit the Whiterose Abbey during The War of the River Kings. After you exit the abbey, just go in any direction, because after a few seconds there will be a random encounter. You will meet a goblin merchant, who will have the throne.
He asks for 100 gold in return. Trying to negotiate will raise the price to 200, but if you manage to intimidate him, he will gift you a lot of useful item as a bonus. The throne is returned.