Go to File > Data and locate the plugin in which you saved when that deletion occurred. Click "Details". Somewhere in that list is the NorBridgeCage02a base object - there should be a D next to it in the deleted column. Select that line, hit delete and hit OK. This forces the Creation Kit to ignore that change when it reload the plugin. The next time you save, the plugin will be modified and the object should be restored.
But it didn't work. Details window now shows no deleted base objects but I still can't use the object and all the cells that referenced it are still flagged with the dreaded '*'.

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