You may be unable to find your receipt because it appears in a pop-up, and your device may be blocking it! However, there's a very simple solution.
Next time you're completing a transaction, you'll notice in the upper right corner a little notifier informing you that a pop-up is being blocked.
Click on it, and it will give you the option to allow pop-ups on this particular page. Select this option. Then, select the link above to access the previously blocked pop-up--your receipt!
Now, all your receipts should pop up following a transaction.