Lost an entire roll because I didn't check the film door latch...
I was at the county fair last summer, shooting with my Pentax K1000. Got some really nice shots of the ferris wheel at dusk and the prize pigs in the barn, probably 24 exposures total. When I went to rewind the film at the end, the rewind knob just spun with zero tension... my heart sank. Opened the back and the whole roll was just sitting there loose, completely exposed to light. Turns out the little latch on the camera door had popped open halfway through the day and I never noticed. That was the day I learned to always give the camera body a gentle squeeze after loading film, just to double check. Anyone else had a similar gut punch from a simple mechanical fail?