Awful. Did not expect edit to by saved until done. Expect a repo somewhere of chart configs? How to view history.
I believe to get chart configs (or any), you would have needed to create a backup in the config files.
if you've ran the panel before, you should be able to check the _audit logs for the time range you ran them to get the search.
Also, in 6.5, the dashboard shouldn't save in Edit mode until you're all done editing and click 'Save'. Are you in 6.5?