With the Socrative Essentials or Pro plans, you can restore deleted quizzes. Here's how:

To recover a quiz, go to your Library tab and click Deleted:

Select the quiz you'd like to restore and then click the restore icon as shown below:

The quiz will show up in your quiz list again! You have the option to Delete Forever here as well. Keep in mind, 'delete forever' is a permanent action and cannot be undone. If you have any deleted folders, they'll also show up here and can be restored the same way.