node.js+mongoose UserSchema findOrCreate

So, I am implementing findOrCreate on my User schema which basically just has and array of profiles (each user can have multiple login strategies). You may take it as a given that a user is positively identified by having a profile with matching provider and id to the supplied profile we are calling findOrCreate with. The goal of findOrCreate is to identify the user that matches the supplied profile or create a new user using the supplied profile. This function has four return cases.

1. Error occurred while querying for user
2. User was found
3. Error occurred after failing to find user and attempting to create one
4. Failed to find user and successfully created one

Now, I believe that the following code does this. My concern and reason for this question is that callback supplied to findOne does not consistently return. If there is an error while querying for the user, we return callback(...) and if we find the user, we return callback(...) however, if we need to create the user, we never explicitly return. Is there someway that I can return the result of the save? Is that even what I should be doing or is this correct the way I have it?

Code:

UserSchema.static('findOrCreate', function (profile, callback) {
    this.findOne({ profiles: { $elemMatch: { provider: profile.provider, id: profile.id }}}, function(err, user) {
        if (err)
           return callback(err);

        if (user)
            return callback(null, user);

        user = new User({
            profiles: [profile]
        });
        user.save(function (err, user) {
            if (err)
                return callback(err);

            return callback(null, user);
        });
    });
});