Q: how can I de-authorize a stolen ipad so that I can restore the number of devices i can load Itunes onto?

I want to remove an Apple iPad which was stolen from my group of 5 devices that I am able to install iTunes on.  The device has not been recovered and the data on it was wiped remotely using the Find my iPad app.  I do not have the device anymore so I cannot physically deauthorize that device.  Please advise.