The query to run on the SQL DB is:
where itemfullurl like '%/
In the LAST row (by Date), the Column ModifiedBy will be the person that deleted the site. Just double check that the ItemFullUrl has ...'Lists/Site Owner/' ... in it. EventType 4 means 'deleted'.
I do not take responsibility for unfair dismissal. ;-)
It is however likely the person that deleted the site.