You can get them back if you can do the following:
1) Put the user back in the Address Book/Directory for a very limited amount of time (just long enough to do this)
2) Use the user’s ID. If you don’t have this, you may have to create a new listing for the user, and substitute the old mailfile (“reassociation”).
3) Set up a “new” Notes client for this user.
4) Synchronize the existing Web address book (hidden in the user’s database) with the new names.nsf on the PC.
Our developers came up with a view and agent to allow our users to see that hidden view and copy and paste into the Address Book in Notes. HOWEVER, it needed some code which is apparently the same sort of thing now used in the synchronization. My steps above are a little tedious, but they should do the job. It’s my understanding that the user’s got to be in the Address Book for the synchronization to work, because you do have to authenticate with a valid OWNER ID. The ID used must not only be in the ACL, but in the Owner’s field under Tools –> Preferences.
Hope this helps! Let me know if you need more details.