A short-lived romance, indeed. The Maroon 5 frontman and the Sports Illustrated model started dating in May, as Us Weekly reported and were seen getting flirty on a June vacay to Mexico. But it ended shortly after, with Levine getting engaged on July 16 to his ex, Behati Prinsloo. "Adam just went MIA on Nina and stopped answering her calls," a source told Us. "He finally told her about Behati in a text message." A source quipped, "She's fine."