How can users recover Vault documents that were created in Vault and lost while checked out in Microsoft SharePoint when using Collaborative Authoring?
Vault cleans up checked-in or canceled files by deleting them from the site, this sends them to the recycle bin in SharePoint. These files are permanently deleted automatically by SharePoint after 93 days.
Following this policy allows customers to recover documents that may have been modified and then canceled or recover an intermediate ending version for a document that was checked into Vault, which was a requirement of the feature.
Microsoft SharePoint Documentation: Office 365 SharePoint Data Deletion