Microsoft One Drive

A client claims that his friend stole his documents by installing "One Drive" on his laptop, and synced all the desktop and documents files from it. That has been going for a few moths.

Besides obviously checking if one drive was installed/uninstalled on the laptop and checking if there are any deleted or existing files in its folder, how can i track its activity and see if it synced any files to the cloud?

Or even better, if someone used its "fetch files" option (https://support.office.com/en-us/article/Fetch-files-on-your-PC-70761550-519c-4d45-b780-5a613b2f8822"

I would appreciate any input on the topic, thank you