If you believe your site has been vandalized, you can check your site log on the activity of your site!
The site log can be found,
You can set a range of dates to narrow the time frame of actions that will be displayed on the page. This can be done by clicking on either of the two fields at the top left of your site logging page. Clicking these expands a calendar - the field to the left of "TO" allows you to set the start date, while the field to the right of it allows you to set the end date.
Note: Site logging will track changes up to 7 days prior to the current date for Advanced plan websites, and up to 90 days for sites on the Ultimate plan. Items older than this will be deleted automatically.