so does anyone have any idea why this happened?
I've encountered this before. It's when you open your last card on another tab, so on your current tab, it still says you have one, but you truly don't, and you attempt to open said card. It can't show you got anything, because that card doesn't exist, but it still goes through the opening animation. If you refresh, it'll show you have no cards.
Customer support service by UserEcho