When a site is deleted by pressing the Delete Site button on the Site Setting window, the site is moved to the Deleted Sites list. It is not actually removed from the account. It can be restored to the active list by making a change to its Settings and hitting Save.
Note that any URLs used by a deleted site are still active URLs on the system. You may need to remove and change any URLs on your deleted sites, if you needed to use that URL on a new site. Just change the URL of the site to be deleted to something like deletedsite1.accountname.v5.pressero.com, where the last four parts of that URL match your Pressero temporary base URL, then delete the site.