@cmost, thanks for the suggestion! I'll try that if MATE's panels ever disappear again in the future. But it turns out I just ran into another problem that required me to delete/recreate my primary user account, which resulted in a properly functioning MATE desktop.
FYI, the problem that required me to delete/recreate my user account was that MATE ceased using my Desktop folder and instead pointed to my Home folder for the contents of the displayed desktop. I recall having seen a setting somewhere in GNOME for specifying to use ~/Desktop as the visible desktop, but I couldn't find it anywhere in LMDE. So the only solution was to delete/recreate my user account. What's the trick for fixing the pointer to the Desktop folder in in case of a future mishap?
Linux user since 2000 ~ visit my blog at DeviceGuru.com