damn.. I know I read it in the wiki just a few days ago.. have never had the same issue myself so I let it pass the memory though..
have a look in the web admin at advanced->configuration->unknown devices
Or devices tree and look for the disk there. Not sure if it creates a device and just disables it. If it is so then..
in the advanced view where you see the device(what you see when clicking the device in the left pane) you will see that ignore is marked.
Untick it, save and reload router. wait a few minutes and lmce should detect it again.
sorry for not being able to give exact answer but at least you have a few pointers to help maybe.(wiki, devices tree, unknown devices)