Meeting reservation vanishing overnight

I have just been given the task of aiding one of our subsidiary companies with domino 6 problems. Unfortunately I have never even seen the domino 6 client. This makes the job a little difficult! Neither do I have access to any of their systems to have a look. A problem has been raised with a meeting reservation on 4th of May being deleted overnight every night. Can anyone give me any ideas on where to tell them to look for the problem? Is it similar to R5??