When rearranging user stories, I find it convenient to group those that are similar under a parent in a given iteration.

However, when I do that, the parent no longer appears in the iteration.

There isn't a way to schedule parent or epic level stories.  The idea behind this is that if there was a need to break a story into several smaller stories, then the assumption is that the parent story itself isn't sized correctly to fit into an iteration in a workable piece.

If the story does fit into an iteration, then the child stories below that should perhaps be tasks instead of separate stories.  There's actually a good post about this in our Best Practices hive on Agile Commons.

So while the parent story does become unscheduled, each child story maintains it's own release and iteration status.  When those child stories have their status changed from Defined up through Accepted, that status is rolled up and displayed in the status of the parent story.

This essentially provides you with a rolled up view on the progress of a very large feature instead of having to check on multiple smaller stories that aren't linked in this manner.  You can see all parent stories and related children listed in a hierarchical fashion by going to Backlogs & Schedules > User Stories.

For your current scenario, the only way around this would be to remove the child stories from any story you need to schedule.  This entails editing each child story and clicking the red 'X' icon next to the Parent selector to remove this field.

Because this removes the relationship between the stories, you may want to add notes to both indicating that they are related or perhaps use the Predecessor and Successor feature to track those links.