calendar items missing after archive

Hi.
could someone please help on this.
I have a user who has archived her calendar.after a while when she
checked in her active calendar , some items were missing. mainly the
recurring ones.

now the problem i know is that recurring items will not be archived but
but the real problem is that it does not appear in her active calendar
as well.
I have checked to see if she has deleted it by mistake but nothing
shows..

upon investigating i noticed that her outlook was checked with caching
mode. made her outlook use caching mode and restarted outlook.
For a brief while i saw the items come back but just as they came it
disappeared.
now the user is complaining of wanting to archive again.
Is there anyone who can help me to find out where those items have
disappeared to and how can i recover them.

i would like to know what has happened here and why it has hapened
after an hour after the archive was performed..

Any help would be much appreciated..

Thanks