Sigourney Weaver seemed to storm offstage on opening night of her new Broadway play, “Vanya and Sonia and Masha and Spike,” last week. Our spy at the John Golden Theatre said Weaver “pulled a disappearing act during the opening-night curtain call.” As actors including David Hyde Pierce took their bows, “All of a sudden, [Weaver] ran off the stage,” our witness said. “Her castmates looked really confused.” But she reappeared in the audience with a bouquet of roses that she presented to playwright Christopher Durang, who was stuck in a wheelchair in the fifth row after injuring his leg. “It ended up being very touching, though there was a minute where everyone thought Weaver had stormed off,” the spy said.