Just to put you in the picture - when you have an operation anywhere, when the incision is made through the skin, the network of little nerves that lie in the top 1-1½ inches is divided. It's highly unlikely that any of the cut nerve ends will be approximated in the wound closure and doesn't really matter anyway as they have an amazing capacity to recreate their networks although nerve tissue grows and heals extremely slowly. With a repair of a major nerve such as in the wrist, it can take up to six months to even begin functioning normally again. But this network of tiny nerves has to recreate itself as well so will take even longer.
I do advise anyone not to be overly concerned about the numbness. It's an inevitable side effect of having a major incision and only (from a medical point of view) a minor thing, albeit annoying to have to live with.