Bookmarks shouldn't have anything to do with whatever objects are in your app - they're a set of selections, and possibly a layout state and location (Depending on toggles). What exactly do you mean by "Unable to see them"? Do they not show up on the Bookmarks list when shared? If so, does this happen when both of these are toggled off?
Note that insofar as location, users won't be able to view another person's private sheet unless they've been given permission to view that sheet (either because it is published or through security rules)