From http://www.webhostingtalk.com/showthread.php?t=1214407
tl;dr:
Confirmed this is indeed an issue. We had someone add funds via Google Checkout / Wallet and then apply the funds to their purchased service. The payment posts to WHMCS and all is green except that the transaction is fake and doesn't show in Wallet. Luckily we verify all orders/transactions.
This happened to us yesterday too. Posting it here for more coverage.