I also noticed that my site was "entered" & "exited" by

wp-admin/index-extra.php
wp-admin/ajax.php
wp-admin/load-scripts.php
wp-admin/widgets.php
wp-admin/load-styles.php
ETC.

This may be a stupid question by someone who hasn't a clue, but if your site was entered and exited by wp-admin doesn't that mean that they hacked your site?