Final answer:
The provided text excerpts do not specify the location of the grandmother on the ship when Iris thought she had lost her.
Step-by-step explanation:
The location of the grandmother on the ship, when Iris thought she lost her, is not explicitly stated in the provided text excerpts. The given passages include various story elements and characters such as Sylvia, the grandmother, the old grandmother, Dame Ericson, and Mrs. Ebbling, among others. However, none of these passages give a clear indication of where Iris's grandmother was during the time she was thought lost. If there is a specific text where this scene is depicted, it would be necessary to refer directly to that text for an accurate answer.