I have a user that can no loger get any history on past reoccuring
appointments. It happened while she was on vacation.
What do you mean by "history on past recurring appointments"? Do you mean
text they entered into the Notes pane of single instances of a recurring
appointment? If so, then making a change to the event that modifies the
entire series, like setting an end date when there was none before will have
that effect. Recurring events are single entries in the calendar and Outlook
generates the individual instances by calculating them based on the start date
and the recurrence pattern. They're not separate entries. If you perform an
action that causes Outlook to regenerate the recurrences, you'll lose all
modifications you made to the individual instances.