SC Back in Stock Notify Me

I sold out on a product JUNE 2. A customer signed up to be notified when back in stock. This app send an email on JUNE 7 and again JUNE 9 to tell the customer the item was back in stock. PROBLEM was, I never increased inventory above 0 since it sold out JUNE 2. Not sure this app is even worth the $5. I may never get that customer back.