To restore a deleted form follow these steps:

1. Go to Site Explorer
2. Go to Forms
3. Under the folders tab click Deleted forms
4. Find the form you would licked restored
5. Press in the check box to the left of the form name to mark the form.
6. Click Restore
7. The form is now restored.
 
If you deleted a form from the deleted forms folder there is no way to recover it.