Law is you have to ship to an FFL holder if going out of your state. Thats it. Nothing more. Don't have to have a copy. Don't have to have the FFL #. Don't have to check anything online. It is up to you to determine how you know it is going to an actual FFL holder at their proper address.

What turns it into a cluster is when a private shipping company (UPS, FedEx) has their own rules they want followed and then their employees interpret those rules even differently than they're supposed to.

Then you get FFL holders that make their own rules (that they are free to do so, its their business) but state they are laws when they are not. That adds to the confusion.