You will need to query your Tidal Master(Admiral) database.  Here is how I write it in MSSQL:

select um.usrmst_name, ml.msglog_crtdt, ml.msglog_text
 from msglog ml join usrmst um on
 ml.usrmst_id = um.usrmst_id
 where left(msglog_text,11) = 'Deleted Job'

This shows you when the job was deleted.  The job name is in the text and gives you the username.

If the jobs are deleted at the parent level, you may not see the child jobs listed.