Suspected bug

Hi,

We have had a few clients recently call us and claim they have paid for their goods online but not received delivery. When we look up their details they show as a lead, unqualified. They give me a transaction number also but it's not on the system.

These people all say they went though the payment and they can remember parts of the payment confirmation page. In the activity tab, the last page they visited was the payment method page also. They didn't however, receive an email from us confirming their order.

In summary, there was no order placed or any reference of it, indeed the customer isn't 'closed/won'. Has anyone else experienced this? The number of users that we have abandon their shopping cart has risen since version 11 and the final page is usually the payment page.