They will grow back if he has lost them.
However, don't conclude that he is missing the claw just because it looks like the molt is missing the claw. Unless you saw the molt, it is just as likely that the claw has become separated from the molt and disappeared somewhere.
If you can actually see his claw caught in the discarded molt, that's a good sign that he was lucky to survive the molting process. This might point to some sort of weakness in the water chemistry. (Iodine? maybe?)