You might have to pull up the AutoSupport in aiq.netapp.com (search for your serial #/hostname). Then click AutoSupport (a little gear on the left), then find the MANAGEMENT_LOG ASUP. In there is an EMS log file. It is the raw file, so it looks like an XML file. However you will see the encrypt event.
If you want to post your serial # or PM me and the volume name, I can probably help you find it.