I too thought you did not get nights for free stays, but my account currently says something like:
Nights Stayed 10
Bonus Nights 18
Now, 10 of the Bonus nights are from my Chase Visa card, but I can't figure out what the other 8 Bonus nights are. And they are strangely equal to the 1 + 1 + 1 + 2 + 3 nights I stayed on free stays this year.
Those are probably from the double nights promotion. Did you stay 8 nights during that promotion period?
I would guess that if an error had been made and you were given credit for the nights of an award stay, that they would show up as regular nights, not bonus nights (though it's never happened to me, so it's just a guess).