If you delete a poll by mistake via admin link you can recover it straight away after deletion.
Simply open the admin link once more and click the button 'Restore this poll'.
You can only do this within two hours after deletion.
If the poll was deleted automatically, it can not be recovered. Once deleted it is gone for good.
According to our policy, outdated polls are automatically deleted from time to time, unless you have a Premium Doodle subscription. All infos can be found in our policy (Outdated and completed polls).
If you want to keep your polls, you have to open them from time to time to reset the timer (more infos in our policy).