I was on a trek in Nepal in 2001, loved it a lot and took loads of photos. This was in the days before I owned a digital camera and, by the end of the trip, I'd filled 12 rolls of film.
When I got home, I had them all developed and was really pleased with the results. Actually, there wasn't a single picture I wasn't happy with. This was more by chance than photography skills.
About a year later, I was thinking back on that trip and recalled a story our trek leader had told us about one of the villages we'd stopped in. This place was high up in the Everest region of the Himalayas. This village was the scene of a terrible avalanche a few years earlier and, on the very spot we were standing, about a dozen people were killed. It was difficult to imagine the carnage of that scene, as they day we were there it was beautiful, warm and sunny. I was really touched by the story and, as we continued on our journey, I paused for a moment and decided to turn back and take a photo of that place, just as a way to remember the people that had died.
So as I was thinking back to that story, I decided to go back through my photos and take a look at that shot I had taken. Actually, I was surprised that I hadn't gone back to that picture sooner, as it was such a poignant moment on my trip. Anyway, it didn't take me long to realise that the photo simply wasn't there. I was certain that all my photos turned out, so where was it? Then I had the idea to go through all the negatives. I still had all the developed photos stored in exact chronological order, so I started cross referencing them to each of their negatives until the "missing" shot turned up. As I held each strip up to the light, I could see that each one was matching up perfectly; nothing missing.
Then I found the shot that I'd taken in that village...and got a cold shiver. The negative that was supposed to be a shot of the avalanche site was completely white. Nothing but a white square.
Obviously, the photo lab assumed this one hadn't worked and so didn't print it out. I still wonder to this day whether it was just a weird coincidence (like something wrong with the film) or something more supernatural at play.
TLDR: Took heaps of photos while on vacation and the only one that didn't turn out was at a place where many people had died.