Well, I had the same problem: some of my items were sold, but I was not payed.
And it is a completely different problem then the one discribed in the "related thread" (where some items were delivered to the customers, but the merchant received a "undelivered"-message and was not payed).
In my case the following happend: a girl bought one of my items, and was charged for it. She received and reviewed (!) the product. When reading the review, I became suspicious, because I knew exactly, that this customer did not appear in my transaction history (it was a friend of mine, who was visiting me a couple of times when I was building the item). So I contacted my friend and she gave me the (8-digits-) order-number she found in her order history!! As you all know, order-numbers normaly have 10 digits now. This specific order definitely didnt appear in my transaction history (not as a delivered, and not as an undelivered item) and I didnt receive the money for this transaction either. Then I checked the reports of the "orders"... and there I found this transaction!!
Im not sure at all, but I think, that merchants are not payed for delivered items with a 8-digit-order-number. I have no idea, why such order-numbers occur, or why merchants are not payed for these transactions. If you want to know, if you are affected by this problem aswell, then you should probably search the orders-report (and not the transaction-history) for 8-digits-order-numbers.
P.S.: I hope my message is understandable, and Im sorry for any mistakes, but Im not a native english speaker...