I had a somewhat odd experience last week too.
My first ever failure to fire. My 45 ACP reload. Tried it twice. Nice solid primer strike both times. When I got home and disassembled it with a kinetic bullet puller it had the proper amount of powder. Punched out the primer and---it had already been fired. Still trying to comprehend how it had a used primer. I keep my loaded rounds in 100 round plastic boxes and my last task is putting them bullet down in the box and looking that all have primers. Pretty easy to spot a missing primer, and I would think a fired one too.
If nothing else, we will both be a little more observant in the future.