Datafiles missing for database

We are on 11.2.0.2...

On querying DBA_DATA_FILE, the file shows an abnormal name as can be seen below -

SQL> select file_id, file_name from dba_data_files where tablespace_name = 'PTAMSG';

FILE_ID FILE_NAME

---------- ----------------------------------------

223 /u03/oradata/CPSFSSP5/ptamsg02.dbf

142 /u03/oradata/CPSFSSP5/ptamsg.dbf

235 /u02/app/oracle/product/11.2.0.2/cpsfssp

5/dbs/MISSING00235

See the file_ID 235 shows the filename as MISSING00235

Also, when checked the file's status, it shows as offline -

235 OFFLINE READ WRITE

Tried to bring it online, but got the error -

SQL> alter tablespace PTAMSG online;

alter tablespace PTAMSG online

*

ERROR at line 1: