My dominant (practically exclusive, actually) nightmare for over 20 years involved forgetting a class schedule or where a classroom was. Initially triggered by the (enormous) middle school I attended for the first half of 6th grade, then it morphed into a whole new set of very-similar nightmares after I started attending college. I'm sure I had thousands of those nightmares. Hell, I so rarely remember any of my dreams on waking these days (used to recall a detailed, ordered history of my dreams each morning, without even trying) that for all I know I'm still having them several times a week without realizing it.

I'd believe thousands of nightmares over the span of a decade, for a traumatic surgery experience.