There may be two different reasons:
The purchase may have not been completed, at least within JVZoo. If the information for some reason is not being sent back to JVZoo, JVZoo has no way to deliver the purchase. You will need to contact the vendor's support desk directly to find out if they did receive the payment, and if they can set you up with access to their program.
Or you may have created a new customer account by entering your contact/delivery email on the checkout page, as that is what creates an additional customer account.
You can review this here: http://screencast.com/t/cefChqIag
This may be the reason why all of your purchases aren't showing up in the back office. If you need assistance finding which account the product is under, simply open a support ticket with us with your receipt information.