Consider the following scenario:
You start Active Directory Service Interfaces Editor (ADSI Edit) in a Microsoft Lync Server 2013 environment.
You connect to a default naming context in ADSI Edit. Then, you locate the Active Directory entry of a user.
You change the objectClass attribute value of the user.
In this scenario, all the data that is associated with the user is deleted in Lync Server 2013.
This issue occurs because the User Replicator service does not read the other attributes of the user when you only change the objectClass attribute. This triggers a delete operation on the user objects.
To resolve this issue, install the following cumulative update:
2987510 September 2014 Cumulative Update 5.0.8308.815 for Lync Server 2013 (Front End Server and Edge Server)