By Rebecca Rosman For 20 years, Dutch art detective Arthur Brand has acted as an intermediary between the police and people who know where stolen artwork might be hiding. Rebecca Rosman for NPR hide caption AMSTERDAM – In his modest IKEA-furnished apartment, Arthur Brand paces to distract himself. "I'm nervous," he says, with the honesty of a man who has learned that bravado is useless in his line of work. He lights a cigarette, leans out the window, and scans the street below. "The waiting is the hardest part." Brand, 56, has made a career out of waiting: for a phone call, a knock at the door, and, every once in a blue moon, a Picasso or a Van Gogh left discreetly on his doorstep. "Those are the moments you realize it's worth it," he says. Until, of course, everything resets, and the waiting game begins again. In another life, Brand says, he'll take his mother's advice and "find a normal job." But in this one, he's helped recover stolen art for two decades — often the cases police can't solve alone.…