Could have caused a rude surprise.
Have you ever been doing something automatically and then had something niggle at you that said you had done something off? I was going merrily along, cranking out 9 mm, when I realized that the funny feeling I had was because at one point my right hand had reached to the wrong spot to pick up a case to seat a bullet in. I had taken out of the bin of primed shells rather than the rack of shells that I had put powder in. A few movements back. And now somewhere in the jar was a cartridge with bullet and primer but no powder.
Oh, great. I put a note to myself in the jar and set it aside.
Finally got around to thinking about it yesterday. I really didn't want to just pull bullets until I found the bad load. Got the scales out and started weighing and looking for patterns of weight within the different brass manufacturers. Weighed every one. The bad one was the second one I pulled. The first one was a 9 mm Makarov that got by me when I was setting primers and shouldn't have been in there anyway.
I'd have been really annoyed if I'd had to knock every one of those apart. And now I'll remember to do what I usually do but neglected to do that day - only keep one stage of loading components on the bench at a time.