It is not possible to see the column names because they are replaced with SYS_Cnnnnn_yyyyddhh:mi:ss$ when marked as unused.

Yes, it is officially an irreversible operation, but if you were to mark the wrong column as unused by mistake, it would be possible to fix with a few unsupported data dictionary hacks.

I've disabled a few columns in a table and I'm now trying to list them somehow. The DBA_UNUSED_COL_TABS views only show the table name, owner and number of columns disabled in that table. How do I list the disabled column names? ... I get the feeling that SET UNUSED may be an irreversible process?