Dear Kristen,
Good day!! Thanks for querying in this community.
According to the description you provided, I have tested the behavior at my end, where I am able to see and access the Sway files in my Office 365 account without any issue and I also checked with the different user accounts in the different tenants, where there is no sign of Sway files missing.
And I checked whether there is any service incident related to the problem described in the Microsoft Service Health Dashboard, where there is no any related incident reported. And we also found several users reported similar issue in our community,
Given this situation, I do understand the inconvenience caused and apologize for it. I recommend you to immediately connect with the related development team, where they can collect all details including the related logs and perform the further investigation from the backend to restore all the data missing from your Sway. So, I request you to connect with your IT admin of your organization immediately (How do I find my Microsoft 365 admin? - Microsoft Support) and raise a new service request from the Microsoft 365 admin center so that the related development team will connect with you and investigate the issue further.
Reference: Get support - Microsoft 365 admin | Microsoft Learn
Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Sukie | Microsoft Community Moderator