ALL of the information available is at www.dropbox.com/events
You can sometimes get the device that did the deletion by restoring the files, going to one of them and clicking on 'view version history' and that will show things.
www.dropbox.com/account shows devices logged in as well as active web pages as well.
One of the BIGGEST causes of this is people just accidentally dragging and dropping a file from Dropbox to something like the desktop.
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