This depends on the cart expiring time. Also depends on how your browser cookie works especially if you are on a PC. For some, it is also because you were logged into your account when adding the items and if you were logged off, then the cart will appear empty. If you log back into your account, you should see your items in your cart still! If you are shopping as a guest, the cart session will empty after a certain time. So being registered/logged in will help keep your items in your cart longer. Hope that helps!