On questions about hours before and after visit to K-Mart, before arriving and leaving his rental room at 10:28 (!), (in context of noon in Henderson, 9:28 (!)), next question is what Steven could possibly be doing in Vegas at an early hour when GW called just before 8 am. SK is already in Vegas.
Two hour drive or so to Vegas? That's up at 5:30am at latest to drive to Vegas on a Sunday morning, if he had returned to his room. No, his room was straightened up. He did that (like being careful to make the bed) before 6am before driving off to Vegas, when his room was normally messy? And that's assuming best case that he had just arrived or was nearing Vegas when GW called.
The odds are that he was already in Vegas when GW called, and that he had done the driving the night before.
Yet he had no change of clothes, didn't bring his cell phone charger, gave no indication he wouldn't be back in St. George Sunday night other than saying he wouldn't be at a church basketball game Wednesday evening, which could be true whether he was in St. George or not.
So other than not bringing clothes and cell phone charger, all other indications are that he was not staying in St. George, at least temporarily, for some reason.
Did he have a car charger for cell phone? No clothes were found in car, but maybe that was what was under his arm or someplace else in Vegas where he had gone prior to 8am?
But didn't take his coat(s), blanket(s), and shaving kit when he left the car.
Always a gotcha no matter what, with only possible explanation being something along lines of fooling people of his real intention, which is explanation of last resort.
Something that makes sense of this will really be amazing.
rd