Thanks, Holly for your response,
To address, there is no recent time security role changes for the user (team/user) and even personal views are used there were no modification done in recent times as per user report.
Coming to the process/plugins, we don't have any associated plugins or processes related to dashboards, but still we didn't have solid evidence of the deletion. To highlight, I can't see tables (userform/userdashboard/systemform) explicitly in the customizations area, but I could see while querying in the backend. However it is fetching details for the logged in user not for a specific user.
Is there any way to enable audit for personal dashboards same as we do for entities?
And regarding the questions asked,
Yes, we have server-side synchronisation with Outlook.
The dashboard is strictly personal not shared with anyone.
There is no third-party integration involved here.
Hope this explains the situation clearer. Please let me know is anything there to track or restore the deletion.