Actually the "Tank" should not be hurt. It's steel. The attached bits can be replaced. Looks like from the empty cap you or the coater removed the insides. Hopefully before heat was applied. The latch is toast but can be removed and replaced. The original latch is hard to come by (expensive) but the replacement locks can be found. The petcock, if toasted as well, can be replaced with aftermarket. I would remove the cap, latch, and petcock if present, and send it back to have it powder coated to match. The other bits you just need to replace. Mark this up to a lesson learned. When you farm work out, don't assume the shop/tech is going to take care of things for you that you should have taken care of yourself.