If you have an issue with the cart where you add an item to your cart, but then it says the cart is empty, please email your order details to me at firstname.lastname@example.org and I'll send an invoice instead. Long story short, if the cart isn't updating, the browser is using an empty, cached version of cart.php. If you're able to force the page to refresh by using ctrl/option-F5 on a computer, it'll show your cart contents. Unfortunately clearing the cache on a mobile device is a good deal more complicated (how to: android | iOS). Worst-case scenario, the cache is time-limited, so if you come back to it in an hour or so, it should show the contents. I'm really sorry about that; it's an all-or-nothing setting, so either all the pages are cached (meaning the cart may misbehave) or all the pages are forced to refresh every time they're loaded (meaning the site will load extra-slowly).