Hi,
Unless you have stumbled across a bug I don't think the content you are creating is actually disappearing - it just isn't visible in the pre-existing slide. This is because slides store the visibility of layers and additionally for a feature collection layer (like Map Notes) the visibility of features as well. So if you are in the mapping activity and you create a new feature in the map notes layer it will be visible in the map; if you then go to the presentation activity and select a specific slide this new feature will not immediately be visible -you need to turn it on. So in your map I selected the final slide, then in the contents panel click the right arrow beside the Map Notes layer which shows me all the features it contains. In the attached screenshot you can see that i've checked on the 'Hurricane Irene, Coney Island' feature to make it visible.
Mike
