The Memcached GET command does not return the expiry: https://code.google.com/p/memcached/wiki/BinaryProtocolRevamped#Get,_Get_Quietly,_Get_Key,_Get_Key_Quietly
Since, GetDocument uses GET “under the covers”, that is why you don’t see the expiry. Apparently you can only set the expiry. I’ll add this to the documentation so that it’s clearer.
Thanks,
Jeff