False/patchy memory

For years I thought I had voted in the 1975 UK referendum on the Common Market Indeed I was 100% convinced I had. Turns out I was wrong . At the time I was on a closed ward during my first hospitalisation. My memory of the period is still patchy to this day. I know I was in hospital and can remember broad details but finer details before and just after hospitalisation eluded me.
I think a first round of ect had a large part to play in obliterating many memories of the time.

I’ve read that ECT can cause memory loss that may or may not come back. Was reading about it after reading that it is considered a top treatment for psychotic depression. The materials said that memories closely surrounding before and after the ECT treatment can be lost.