Since history management is not performed, it can not be returned.
If it is a dashboard which is included in default of apps, the original remains in the default folder. Newly created or modified parts will be overwritten.
You may be wondering how this happened and I have a warning. If you comment out a panel using <!-- syntax, and then you rearrange the panels using the gui mode, splunk will rudely delete ALL OF YOUR COMMENTS and you will lose your hidden panel.
You cannot get the XML back but usually the part that is broken is the SPL and you should have at least 15-days worth of index=_internal search=* logs that you can dig through to find the searches that your dashboard has been running. This has always saved the day for us.
Since history management is not performed, it can not be returned.
If it is a dashboard which is included in default of apps, the original remains in the default folder. Newly created or modified parts will be overwritten.
