When Alex woke up there was nobody in the room with him and the healer had seemingly done everything he needed to considering the state of Alex's left hand. The damage had been completely healed from a visual perspective but there was still the risk that his hand wouldn't be fully functional.
Like every other User in the lower cities, the healers were at most E rank and this meant their power had limitations that the more powerful healers in other cities didn't have. It was common for an injury to only be partially healed and in some cases the only thing the healers could do was heal the injury from a cosmetic point of view, leaving the damaged area without functionality.
Alex tried to open and close his hands a few times, comparing the left and right in how they felt. His heart dropped when an obvious disparity between either hand was felt, the injury was definitely not healed completely.