I'm having this issue too, just had the Cow and milk fair I entered Excellent quality Golden Milk (the game wouldn't let me put my cow into my inventory for some reason) I spent all day at the fair, the Mayor came over and judged the milk several times, exclaiming that the Golden Milk was the most wonderful thing she had ever seen. I then got a notification that the fair was ending, once it ended there was no notification about the winners or if my sim had won anything and to boot, the milk had vanished into dust, along with the rest of the fair.
I hope this bug gets fixed soon.
