Contact disappeared, Contact notes disappeared

Hi,

Recently an administrative assistant reported that a contact item had
disappeared from her bosses Contacts folder. She is sure that the item had
been there before. She has delegate (editor) permissions to his Contacts.
Both are using Outlook 2003. The server is Exchange 2003.

In a separate incident, the administrative assistant reported that
information that she had entered into the "notes" area of a contact item had
disappeared. I was able to recove this info from an old copy of his Contacts
folder, so I know that the item did contain it at one time.

Aside from someone purposely or accidently deleting the contact, or the info
from the notes area, what could cause this? Any suggestions on how to
troubleshoot it?

Mike