Hi raging vortex. Have you considered consulting with a neurologist or maybe neuropsychologist on this? It may be unrelated to a mood disorder. It might be good to know either way. If it is a psychiatric concern, do bring it up with your psychiatrist and therapist, too. Maybe some form of trauma was involved, so you're blocking it out? Did you used to remember?

I have experienced "manic" blackouts and memory issues associated with ECT, but they didn't affect my long-term memory and the issues eased as my mental situation did. Severe illness and some meds also caused some cognitive dulling in the past, but never so severe to forget major things. That dulling passed.