I've missed many dives for many reasons, including weather, illness, and equipment failures. In fact, I missed my last scheduled dive when the SPG for my backgas started to bubble just as we were getting started in descent. There were three of us with limited time, and it was lonely watching the other two head down for a great dive whilst I went back to fix things up.
The most maddening miss came only a few months ago. I was with a group of people in a very remote spot, on our last day there, and for reasons too complicated to describe, I ended up sitting and watching while others dived while I waited for the time I could finally get into the water and do my planned dive. (I had to get the right combination of people for that dive.) During that time, the people who were finishing their dive days packed up, said their goodbyes, and left.
Finally, the only people left were the ones with whom I was supposed to do that very special dive for which I had been so patiently waiting for so many hours. We went to the entry point, but when I went to pick my fins off the hook on which they were stored, they weren't there. The only pair of fins there were someone else's.
One of the people who had departed earlier had mistakenly taken my fins and left his, and they didn't fit me.