Depends what you mean by fairly large. If you had initially fitted it back on exactly in place all around, then splinted it on well to withstand winter winds, it's possible that it might have taken by spring, but it's too late now, and there's nothing you can do but cut it flush with the trunk as you would any branch cut off. It's also not going to 'root' for you as it's the wrong time of year, but also because Japanese maples are quite hard to root at any time and most people don't bother trying.