We use the People section on the To-Do Bar in Outlook 2013 to quickly view status & communicate without switching to Lync. I have a problem with certain contacts disappearing from this list every time they are added (by using the Search People box then right-clicking and selecting Add to Favorites) . It doesn't need a restart or anything for them to disappear--they are gone later in the day. Some contacts never get deleted. I've tried adding/re-adding the problem contacts to Outlook & cleaning up duplicates, etc. but have not been able to pinpoint the cause of this issue. I haven't found anything that separates the contacts that stick with those that get dropped. These contacts are local domain members also using Lync 2013, Outlook 2013, and Exchange 2013 (which is in a separate resource forest).