On March 1, the day after the first coronavirus death in the United States was announced, brothers Matt and Noah Colvin set out in a silver S.U.V. to pick up some hand sanitizer. Driving around Chattanooga, Tenn., they hit a Dollar Tree, then a Walmart, a Staples and a Home Depot. At each store, they cleaned out the shelves. Over the next three days, Noah Colvin took a 1,300-mile road trip across