Sidewalk shopping in NYC can yield a bounty of recycled Ikea furniture, designer duds, and even priceless records. So in 2003, when Upper West Side resident Elizabeth Gibson spied a discarded painting in the trash during her morning walk, she knew to do a little more digging. And what better place to see if your family heirloom really is an original masterpiece or just some worthless trinket Grandpa Joe picked up in the South Pacific while on shore leave than on PBS’s Antiques Roadshow? Gibson discovered that the piece was not only by celebrated Mexican abstractionist Rufino Tamayo, it was also on the lam! The work had been pilfered from a Houston collector’s warehouse in 1989 and hadn’t been seen since. Last night the painting sold at Sotheby’s for a little over $1 million, which will net Gibson a $15,000 reward for returning the piece along with a percentage of the sale. Sure beats dumpster diving with Freegans for bulgur wheat muffins.