A twilight landscape by Jasper Francis Cropsey came with a metal tag bearing the artist's name and two crosses, an element adding to the painting's value and authenticity. When Alex and Laurel Acevedo of Alexander Gallery went to set up their show booth, the metal tag, waiting to be affixed to a new frame, had been swept away to the trash. The couple raced to the nearest dumpsters and offered a hefty $10,000 reward to anyone willing to find the "needle in a haystack"...