I expect Rudeus to get his hand back at some point. The reactions to his missing appendage were exceptionally mild, if you ask me. Sylphie didn't even comment on it at all, if memory serves. It seemed equal to a soldier in our world coming back from a dangerous mission missing a few teeth. Must have been painful and a testament to the hardships suffered, but a visit to a dentist will see it fixed in such a manner that nobody will notice the difference afterwards.