A new mishnah! One who finds documents - bills of divorce, papers that free slaves, receipts, etc. - don't return them to the apparent recipient, in case they weren't actually given. Also, when the documents include names belonging to more than one couple - especially in a place where the caravans pass frequently vs. a place with few travelers, and less likely to find two couples of the same name. Plus, the question of whether she has received the ketubah... did she already receive her get? That may well depend on what the husband has to say - and maybe the time factor in how long since the get has been lost. Note that the dispute here is between texts, where the mishnah outranks a beraita.