Wicker Park (2004)

Matthew, a young advertising executive in Chicago, puts his life and a business trip to China on hold when he thinks he sees Lisa, the love of his life who walked out on him without a word two years earlier, walking out of a restaurant one day. With a little help from his friend Luke, Matthew obsessively and relentlessly tracks Lisa down and while doing so, runs into another young woman calling herself Lisa whom, unknown to Matthew, is an actress named Alex and may hold the key to Lisa's disappearance, and discovery.