I did exactly the same thing a few decades ago, Dana...shot a gobbler and also accidentally killed an unseen hen beyond him (related this story recently in another post...gladly turned myself in and paid the fine). Like you, I also know of a couple of other guys that have inadvertently killed hens in the spring.
It would be interesting to see how many others have had a similar experience. Honestly, I suspect it happens more than any of us would like. In today's declining turkey populations, it is probably a statistic that may be having an impact in places. As you say, mistakes can be made, but it would be nice if those making the mistakes would speak up and report their error and "pay the piper" so wildlife managers could assess that impact. Unfortunately, I am skeptical as to how many do.