11top
Cousin Eddie's cousin
Sorry to hear about the damage on this one, it's a terribly bad surprise especially when there is otherwise no obvious sign of trauma on the outer box...
That said don't be too hard on the seller because what you describe above is exactly how every single SE, Core, and Private Stock guitars I bought was shipped by PRS to the dealer (and thus from the dealer to myself).
There was one exception (Music Store Live I think) where they double boxed, but other than that it was always the hardshell case inside a box with hardly any room for padding (and thus no padding) on the sides, and then just the tiny piece of 4x10 bubble wrap on both ends as you describe. I don't consider that optimal either, though it happens to work out well enough on average...
I think that’s the key. Was the guitar shipped to you using the standards set by the manufacturer? I’m confident PRS knows how much protection is required for the care and handling expected from the carrier. If those standards were met, I’d say the responsibility is on the carrier.