After reading the second chapter, I learnt that the writers didn't forget that Luke had lost his light saber in episode 5 after all. His original weapon was his father's but he lost it in a dual with Darth Vader when his hand was cut off.
In The Return of the Jedi, Luke had gone back to Obiwan's home to construct his own light saber from the spare parts found there. He did this before heading to Jabba the Hutt's palace. So how does he even know how to make a light saber? That's not suppose to be relevant in the story I guess. :-) Anyway, let's get back on this journey as Luke rescues his friends from Jabba. Till the next post....