This is definitely Campo Santo's.

Developer Campo Santo can take pride in the fact that its Firewatch art captured the spirit of the wild so perfectly that a Ford dealership stole it for a sales event. Alas, I fear that even with 0% interest, the Ford Freedom will prove a poor match for the scree and cave systems of Shoshone National Park.

For the avoidance of doubt, allow me to credit the ad to Quirk Ford. Well, the bottom half of it. The art is the work of Campo Santo's Olly Moss. And the screenshot is by Kyle Daigle, via Firewatch co-producer Panic Inc. Everyone acknowledged? Phew.

Campo Santo has responded with wit, if not good humour. No acrimonious copyright suits to see here.

Come on down to the Quirk Ford Freedom Sales event where ur free from such things as "copyright" and "infringement!" https://t.co/78HMQdyJqyJune 27, 2016

Speaking to Game Informer, Quirk Ford said the image was taken from a wallpaper site—a wallpaper site that does not guarantee the provenance of its images. Furthermore, Vanaman pointed out that some elements of the ad could only have come from an old Campo Santo website.

Quirk Ford has since apologised, and the fire is out.