When i first went to adjust it, it was frozen. Not wanting to risk breaking it, I called Lakland and asked their advice. The tech on the ihine referred me to Carl Pedigo, evidently a highly regarded luthier in Chicago. He advised me to remove the neck and then remove the nut from the truss rod. Once I got the neck off, the nut unscrewed relatively easily, at which point it came off after only 3 turns. There was 1/4" inch of truss rod, the end being pointy and rusty. It obviously had been broken long before, and a different nut attached.
Why didn't you just contact the seller and ask for a refund the moment you realized that the truss rod was frozen?
The seller can successfully argue that you broke it because you took it a part (removing neck and nut). A person with no knowledge of the workings of the bass will agree with the seller because they would think only a qualified person should be doing repairs.