I used to be a music teacher, and couldn't tell you how many kids showed up to their Christmas or spring concerts without an instrument. Makes me wonder what the parents were thinking, driving them to school for a band concert with the instrument sitting at home!
But I shouldn't be one to talk. Playing in sometimes three or four ensembles, I've shown up to a rehearsal with the wrong music folder.
No really strange reasons, just the usual obvious stupidity of forgetting film. (etc.,etc. )
But I've been thought a bit odd, or too much of a perfectionist, by non-photographer friends when I've not taken an otherwise good shot because of a litter bin or trash can in the wrong place, or when I've gone to move a piece of litter from the front of the scene I wanted to shoot.
I had a friend at university who prepared and showed up to write an exam for one history course only to find out that he had switched the exam times, and had to write the exam for another course.
Again not photography related, but this thread reminded me of an elderly teacher I had at middle school who admitted that she had once gone all the way from her house to church on a Sunday morning carrying her kettle instead of her handbag.