Once a job has been added to the system it is possible to find out who entered it.
Firstly bring up the job details
Click on 'Job Address Details'
You should now see the job address details, account number etc. On the right you will see 'registered on system by' next to that will either be a user's name, or 'unknown'.
If a user's name has appeared it was this user that entered the job into the system, however if unknown has appeared then there was a problem when entering the job and no name has been saved.