corrupt file n block associate segments not showing up

I am not getting any data for the block n file number shown as corrupted  in database ..why ?

SQL> select distinct file#,block# from v$database_block_corruption;

     FILE#     BLOCK#
---------- ----------
         4    3749450
         4    3749458

SQL> SELECT tablespace_name, segment_type, owner, segment_name
   FR  2  OM dba_extents
     3  WHERE file_id = 145
  4     and 3749450 between block_id AND block_id + blocks - 1;
SELECT tablespace_name, segment_type, owner, segment_name
   FROM dba_extents
   WHERE file_id = 145
   and 3749458 between block_id AND block_id + blocks - 1;

no rows selected

SQL>   2    3    4

no rows selected