Remove licenses from deleted user on OS X Server's VPP managed distribution

We buy apps using Volume Purchase Program with managed distribution through OS X Server's profile manager.

One of employees left, so I removed his user account from OS X Server. However, the licenses for apps we bought him are still unavailable to re-assign to other users, and I can't remove them from his account manually because it has been deleted.

Viewing the app's info page in Profile Manager shows that we have 13 - 3 = 10 licenses in use, and only lists 9 people who currently hold licenses to the app:

Is there anything I can do to reclaim that license? I could re-create the user, but we don't have access to his Apple ID so I don't think we could re-connect it to our Profile Manager; and if we can't do that, I don't think we'll be able to see the app associated with his user.