DATA: Data. Yes. We were on a ship together.
[What else would you think? She looks exactly the same as she does in the 24th century. And a black woman hosting a literary reception in 19th century America is not exactly a run of the mill event. In fact, it's so suspicious that it only makes sense that it would be "his" Guinan. Would you have super-smart Data follow this line of thinking: "I just time traveled here. Oh, there's Guinan. But it cannot be Guinan because time travel is impossible!" ???]