Re: ATF: North Trail - short circuit
What are you measuring with the ohm meter that shows a short circuit?
If you do have a short, you should have a blown fuse, not a dead battery.
When the installer attached the retainer to the side wall of the trailer, it's possible one of the mounting screws could have hit a wire inside the wall, but that would normally take out one 12V fuse and the stuff powered through that fuse.
Often batteries go dead on dealer lots because of the parasitic drain from alarms, radio control panels, etc.