I just wanted to give everyone a heads up on this, because this issue is ongoing and seems to be getting worse, though not necessarily in frequency, just in how eBay / PayPal are handling them.
Previously, when a buyer attempted purchase and payment and the payment failed, while I did get payment notifications, either the order wouldn't show up on eBay, or if it did, the payment status showed as refunded, so I could be alerted that there was a payment issue.
Today, however (and who knows when else, I haven't done a thorough check, yet), I received the order, I received the payment notification, order status was normal, remains showing as paid, but I found it was reversed when I logged into my PP account tonight.
Lucky for me, it wasn't a huge sum (this time, anyway), so if I can not recover the funds it won't break the bank, but I'm not particularly happy this has been happening for weeks and neither eBay nor PayPal has developed any kind of alert for failed payments, but in fact made it more difficult to detect. 
So, yeah - a warning and advice to perhaps double-check before making the trip to the PO.
It looks like the proper status shows on the full order details (which I don't usually access when processing orders), so either log into your accounts to check payment status(es), or keep an eye out for this red banner:
