I did the same thing with 9mm a while back.
Got back into reloading the last few years.
I don't use a progressive, but I was doing a fill and bullet seat and got lost.
Now I fill them with powder, look into each case and then proceed.
I actually had tow out of that batch. Same drill, dowel down the barrel cleaned it then stopped, took them home and weighed them to see if they had powder in them.
For me I am not good at remembering if I looked at each one so single loading is better for me.
ps: my brother who is very meticulous (progressive loader) had a couple of duds with his rifle reloads. Same thing. We were both talking about it and he admited it first. I told him, well, I don't feel so bad!