Am I the only one who can't find invoices from Fab?

You need to hide your order id, other people might used that as refund with the seller.

Check your mail, it should come from “help@acct.epicgames.com” and title start with “Your Epic Games Receipt”. Inside the mail, you should see an invoice id.

Or contact support for further help: support.fab.com/s/?ProductOrigin=FabSupport