What causes a receipt to not be issued?

Hi all,

I frequently keep tabs on what's on my bank and card statements to see if there's anything out of the ordinary.

Usually App store and hardware purchases are really easy to keep track of since Apple almost always sends a receipt email (except for that weird time around a year ago when people were having issues with that, including me).

I was doing my routine check and I found an Apple purchase, but couldn't find a receipt email. Nothing in my spam folder either. I was about to sound the alarms, until I checked my purchase history with the help of this page. I found the corresponding purchase, but usually, when you click on it, it shows you a receipt with the billed card, billing address, etc.

On this purchase, it just says "This purchase doesn't have a receipt". So, as someone who keeps close tabs on receipts and invoices, what causes a purchase not to have a receipt and how can I extract a receipt if I can't find one in my purchase history?

Cheers!