DBMS_ROWID problems

 I'm trying to write a PL/SQL program to return the data values from a locked row to help our developers debug the locking conditions.  However, I'm having lots of difficulty with the dbms_rowid package.  I get the columns ROW_WAIT_OBJ#, ROW_WAIT_FILE#, ROW_WAIT_BLOCK#, ROW_WAIT_ROW# from v$session for the locked row and use the dbms_rowid.create_rowid to create a rowid from the values.  However, when I try to select that row I'm getting an ORA-01410 Invalid Rowid.

When I write a bit of PL/SQL and select the rowid of the data row I've locked, I get a slightly different rowid format, but it's largely the same.  However, I cannot resolve the parts of that rowid with the dbms_rowid.rowid_info procedures.