FOR DECADES,A major piece of counter-culture history was wedged behind a bed in Merl Saunders’ San Francisco house. The crude pipe looks like something a teen may have cobbled together at summer camp, but according to art historian Steve Cabella, it’s basically a religious object. A so-called “spirit pipe,” this particular pot implement was made by LSD pioneer Augustus Owsley Stanley for Grateful Dead frontman Jerry Garcia, & it’s been MIA for decades. “I’ve bought party pipes from rock people before,” Cabella — owner of California antiquities shop The Modern i — tells Rolling Stone. “They’re just funny little things;...