Lync Address Book Weirdness

So, I'm at a fairly large client that's moved from Lync 2010 to 2013.  The server-side migration completed a while ago, and the client migration is in progress.  Enterprise Voice is enabled for a select group of people.

Some people have noticed that when they search for a specific Lync user, the only object that got returned was an object for their Active Directory administrative account that had only a phone number defined (not a Lync-enabled account).  The Lync-enabled "normal" Lync entry didn't show up in the search, even though it did appear in the GALContacts.db file (the Lync locally cached address book file).

The really weird thing was that the object showed up like a phone contact object, but one that had presence working.  The affected user could toggle their presence, and the contact object would dutifully change itself.  However, since it wasn't a Lync object, you couldn't start an IM (but you could call the associated number).

This user's first name isn't actually "Admin" in case you were wondering.

Another weird thing was that the very first time you pulled up that person's name from a search, it would briefly show the proper Lync-enabled account, but switch to the phone contact object view after a half-second or so.

Yet ANOTHER weird thing, was that after viewing the admin account object in Lync a few times, usually after viewing the contact card, the next time I did a search for the same name, only the phone number appeared.  However, I could still look at the contact object for the phone number and it would show the user's email address.

As mentioned previously, the address book had the correct contact information (verified by opening the GALContacts.db file in Notepad....the results ain't pretty, but it works), as well as the information from the AD admin account, but Lync was choosing to show the non-Lync enabled admin account in searches.

When I compared the affected admin accounts with others, I noted that some users showed up properly, but others didn't.  More comparisons showed that for the incorrect information to show up, the following had to be true:

1. Both the Lync-enabled account and the AD admin account had a phone number defined
2. Both the Lync-enabled account and the AD admin account had the same email address defined.

Removing the email address from the admin account, re-generating the Lync address book via Update-CSAddressBook, and re-downloading the updated address book file fixed the issue. 

So, what happened?  When you do a search, the Lync client will look at the address book, your own Outlook contacts, and any social connectors you may have associated with Outlook (like Facebook or LinkedIn).  If the same name shows up in multiple places, Lync will try to consolidate all the information and show only one contact object.

Sometimes, the process goes awry. In this case, it appears that Lync saw the same email address for both the Lync-enabled AD account, and the non-Lync enabled AD admin account, and incorrectly presented the non-Lync enabled account as the single object.

I'm guessing this is a bug, because Lync really should place priority on a Lync-enabled object over a non-Lync one for presentation.