If you are hosting with us, we take multiple backups of live surveys everyday. We retain those backups for 90 days after the hosting project's closing date. So if you are hosting with us, you would be in luck. Send an email to firstname.lastname@example.org with the details for your project and we will work with you to get the deleted data.
If you are self-hosting, there isn't anything that we can do, unfortunately. If your system has any sort of backup process, it might be possible to retrieve some data from there.