As we all have seen, the Force Awakens is featuring a blue Lightsaber. Now the most common speculation I have heard is that this is none other than Anakin Skywalker's saber. Let's break down the facts we know to figure out if this really is the Saber that massacred many Jedi. First, we know that Luke lost his hand on Cloud City over the planet Bespin. Still in his grip was his father's saber. Now, Bespin is a gas giant that is far too poisonous for humans to be able to even try surviving there. ( http://starwars.wikia.com/wiki/Bespin ). So to me, this takes all the possibilities of the Empire going and getting the Saber off the planet surface. Yes there are droids that may be able to survive the surface and possibly even other alien species. But some food for thought. Would the Empire, in the middle of trying to crush the Rebellion, waste time and resources searching for a Lightsaber? If the Emperor is waiting for Luke to finish his training before trying to turn him to the Dark Side, would they bother with the other Saber? In Episode VI: Return of the Jedi, Darth Vader sees Luke's new Saber and makes a point of saying that his training is complete. Would they really have bothered with it knowing that this young Jedi was going to end up making his own? Which brings me to my next major point. The new Saber of Luke has a new feature: a green blade.
Knowing that this was happening, there was never a point where they needed to recover the Saber. Darth Vader has his own Saber and of course the Emperor has his, though he apparently doesn't keep it on his person. Even all the Inquisitors we are seeing so much of lately have unique Sabers. Yes in the original "Canon" of the series they make a clone of Luke and train him in the Dark Side using the hand DNA to make the clone. However, we know they are trying to differ it from that train of thought. Is it possible that what we see is the Saber of Skywalker? Yes. Is it? Probably not. I believe that Luke has built another Saber for his children, who you see being given the Saber (assuming it is his child). The Emperor comments in Return of the Jedi that Luke's new Saber resembles that of his fathers. To me it shows that he is quite capable of replicating Darth Vader's Saber. Also, if the Empire acquired it, then how is it possible that the Rebellion acquired it with Luke not fighting to raid the Death Star while dragging Darth Vader onto the landing craft before the station blows up. Think the theory is crazy?