Looking for files in the .atlassian-companion when files cannot be uploaded (lost connection, closed browser window, Word crashed, etc) is not something a regular user would do. This is to complicated.

reference:

https://confluence.atlassian.com/confkb/how-to-access-confluence-files-edited-with-the-atlassian-companion-app-955178822.html

The Companion app should know where the last version of the file was closed and if it should resume editing of that file next time the user wants to edit it. 

Or even better, auto upload regularly (autosafe) to the Confluence page. One could then be asked to either open the autosaved version, the one on your computer (if the same user) or the latest uploaded.