on this? Luke's hand was cut off a good couple minutes before he steps off the gantry. Where it goes, we do not know. It is not with Luke as he falls, it is not with Luke anywhere in the specific debris-clearance tube he slides through. Watch the first ten seconds of this. In slo-mo. When the doors open, nothing falls out except Luke. As he falls to land on the weathervane, nothing falls with him. He lands on the crossbar and nothing falls past him. He looks down and sees how much nothing there is under him, as well as a piece of debris. Any place that has ventured an ID has held that it was part of the weathervane, broken off by Luke hitting it. No official source as ever said it was his hand/the lightsaber/both.
I had always wished that he had it on his belt when he went into Jabba's palace, only to have it confiscated when he was captured, and then the reveal that he had built his own would've had even greater impact. I remember, at five, when I saw ESB, registering Lando saying the Empire was taking control of the city (cue citizens panicking, including ice-cream-maker guy). I just figured it was too dangerous to go back and retrieve it wen I didn't see him with it in ROTJ. I never
felt it was "lost".
I'd also like to point something out I think a lot of people miss. Cloud City is a bit over ten miles across. Ten miles
. That central spar and repulsorlift bulb are big
. Whatever is still visible falling that far is probably substantially bigger than a hand clutching a lightsaber. And what is the "fluttery" bit hanging off the rod-shaped bit? Luke's hand got cut off clear of his sleeve.