Communication & service is terrible

Ordered the new KFC masala boxes @ 20:50. Food was supposed to be ready by 21:23 & delivered by 21:38 checked on the app from 21:23 & my order was not even collected, try to call the number provided on their app and it just cuts. I sent an email by 21:45 & I get a response saying there was a problem with delivery and they will investigate, I then get another email stating the restaurant did not have stock! This was way after 10. How does a restaurant accept an order and not have stock? Also why did I have to so the emailing & calling when I could've been advised by Mr D that there was no stock- could the driver not have informed them? Could they not pick up on the app that the order is taking longer than usual??