Dear Zoe Bailey
Welcome to the Microsoft Community, we are glad to assist you.
We understand that you are experiencing an unexpected rollback to a historical version of a file in Teams, and in order to better assist you, we need to confirm some information with you.
Are you using a school or business account, or a personal account?
If you are using a school account or a corporate account, the corporate version of Teams has an archive feature, so you can contact your school's or organization's IT administrator to assist you in archiving your files.
If you are using a personal account, unfortunately you can look in your personal OneDrive to see if there is a historical version of the file that was uploaded.
If you have uploaded a file, you can try to find it in OneDrive.
Find lost or missing files in OneDrive - Microsoft Support
We hope that the above information has been helpful to you. Please feel free to reply if you need further assistance.
Thank you for your understanding and patience and I look forward to hearing from you.
Best Regard
Tracy | Microsoft Community Support Specialist