Collaborative authoring connects Vault to Office 365™ to allow multiple users to edit a document at the same time using the Office desktop software, Office Online™, the Office mobile apps, or in a browser. When the user tries to click on the 'Edit in Microsoft office' option to do collaborative authoring gets the error as attached.
The document is manually deleted by someone that's not a Vault Collaboration which goes against how the Collaborative Authoring process is supposed to work.
To check who deleted the document in Sharepoint, the admins can go to the Recycling Bin and see:
In regards to restoring an item from the Recycling Bin, here's an article for that:
Restore items in the recycle bin that were deleted from SharePoint or Teams
Microsoft Articles :