Sandbox plugin deactivated and deleted, preview still showing sandbox preview

I am still showing the sandbox preview in administrative mode, despite the plugin being deactivated. Shows fine to the public but I get an error when logged into dashboard on wordpress when trying to access my home page, stating

“Index of /sandbox/SandboxTest1

Parent Directory
wp-content/
wp-includes/
Apache Server at tulleandtweedphotography.com Port 80″

I am deleting the sandbox folder from my ftp now, but not sure what else to do to remove all content. Please help!