check if the sql used some other sql_id in hiostory and way to prevent that

There was a problem 2 days before that a job running fine other days was tsaking a lot of time.

The event on which it was waiting was db_file_sequential read.The rows_processed from v$sql were 0 event after 2 hrs of starting the job.

I checked the previous excution plan as below:

SQL> select SQL_ID,PLAN_HASH_VALUE,TIMESTAMP,REMARKS,time from dba_hist_sql_plan where  SQL_ID='9j4x3uv6w6t0m' order by TIMESTAMP;

SQL_ID        PLAN_HASH_VALUE TIMESTAMP           REMARKS                              TIME
------------- --------------- ------------------- ------------------------------ ----------
9j4x3uv6w6t0m      1214502413 08-13-2013 21:34:17