PARIS—Shortly after returning Leonardo da Vinci’s most famous portrait to its home at the Louvre for the second time this week, Interpol officials admitted Wednesday that a full 89 percent of its work involves locating and recovering the Mona Lisa. “When we’re not busy tracking down a burglar who has just stolen the Mona Lisa, we’re usually staking out the compound of a black-market art dealer trying to sell the Mona Lisa, or infiltrating a crime syndicate actively planning a Mona Lisa heist,” said Secretary General Jürgen Stock, citing the dozens of times per month that Interpol agents in search of the painting typically give chase through the Paris sewers, stop Moscow-bound trains to search the first-class compartments, or put out an urgent alert to their counterparts in the Swiss Alps. “Every few days, we’re off pursuing another thief in another part of the world. Sometimes we’ll put the Mona Lisa back on the wall, turn around, and within minutes it’s gone again. If we’re lucky, we can sometimes get it back before anyone notices, but that’s rare.” At press time, sources confirmed the Mona Lisa was missing.