I called Cox Tech Support. He was very helpful, ran some kind of reboot/reset, but half of the recordings are still gone. He offered to schedule onsite visit to further debug and if needed, replace the DVR. However replacing the DVR will cause all the remaining recordings on that DVR to be lost, so I am opting to continue as is and hope it doesn't reoccur.
Suggestion: Offer some sort of backup capability for Contour DVR hard drive, so it can be stored in the Cox cloud and protected by Cox. What would we ever do if we couldn't back up our PC hard drives, in case of a hiccup?! Yikes!