The 4-foot-high, 100-pound, fiberglass-reinforced cement bust of Snowden, who is living in exile in Russia after divulging secret U.S. government collection of phone records, turned up on a monument that honors American captives who died on British prison ships during the Revolutionary War. The three artists say they considered the bust “a gift to the city” that could spur discussion about American ideals, values and heroes. Parks officials and police didn’t see it that way.