Yeah that totally happened. I play in a lot of Schwarze draft leagues, and his policy has always been that you can edit picks as long as the next person hasn't picked. But if you have a different policy, that's fine. Looking back at that pick now, it seems from the timestamp that Heat made his pick while I was editing, and that by the time I hit submit, his pick already posted.
I tend to waffle a bit on picks, but knowing your policy now, I won't post until I'm certain.