MAYFIELD, Ky.—On the day before Thanksgiving, Mayfield Consumer Products in western Kentucky posted photos online showing smiling employees lining up at a buffet table ready to enjoy a special pre-holiday meal together in the factory canteen. On Friday night, the candle-making plant where workers had celebrated two weeks earlier lay in ruins, flattened by a devastating tornado during a late shift as more than 100 employees toiled inside. The next morning, 40 of them had been rescued; many of the rest were missing. The tragedy came as Mayfield Consumer Products, which describes itself as a local, family-owned maker of candles, wax, and home fragrance goods, was seeking to expand its workforce, recently advertising job openings on its website and Facebook page. Search-and-rescue teams on Saturday combed through the debris of the tornado-ravaged factory on the west side of Mayfield, a picturesque town near the confluence of the Ohio and Mississippi …