Technically it was a 3rd party seller right? Like eBay or a flea market or the back of a truck?
Yes, but you still pay Amazon, and Amazon pays the seller. Using a virtual card wouldn't have helped him here. The other victim wouldn't have been helped by using a virtual card at Walmart.ca either.
A virtual card that expires or is limited would have protected somewhat.
No, because the order would still have gone on Walmart.com with his real name and address
There are no virtual card options
Technically, yes. But Amazon's site doesn't make this clear.