This is not responsibility of the dealer or delivery service. It is a manufacturing defect. It may have been just fine when it left the dealer's lot and the problem occurred when it was on the way to you. Keystone is reponsible for the warranty, not the dealer.
I highly doubt that that small crack is the cause of your issue. The slide out mechanism is not dependent on that one small bolt to bear the weight of the slide. It is either welded to bolted to the frame. I would suspect that the slide just needs to be adjusted. You can contact any Keystone dealer in your area to verify that they will service the rig since you bought it out of state.
Even though the mis-adjustment may have occurred during transit to you, it reiterates the need for a very thorough pre delivery inspection and customer walk through when purchasing a new recreational vehicle. Over time, you will find additional problems that will need to be addressed. You will either need to take it back to the selling dealership, or develop a relationship with a dealer's service department in your area.