If you're talking about bonus data that you received by signing up with autopay (some promos have even 1G + 500MB) that is added to your monthly data. You won't see a counter on the side as said above because it is just part of the total.
It should be on the Overview section on the right of your account.
I am assuming it was the More is Merrier free bonus for data and LD minutes.
@Ehc If you have any left it should be on the main page (overview page )
Try again incognito/private mode
And or lap top /computer
simply try refreshing the page to check data plan / mins / add ons
For most up to date account info