Event triggers during customer signup

Hello all,

I am making a "Send SMS" extension for my store whenever a customer sign up.
As opencart provides two ways for a customer to signup:

1. Create a account link
2. When customer tries to place new order, then customer sign up.

I am using below code for triggering the SMS event in my VQMOD...
This works well, when customer sign up from "Create a account link", but event is not triggered when customer sign up by 2nd method (as stated above)

(OPENCART VERSION 1.5.6.4)

Could somebody please help here..

Thanks