Just wondering if you covered or not... 28 degrees would have likely zapped many of the opened flowers but plants would soon have a bunch of replacements.

I did. I THINK it helped but hard to tell because it warmed up a lot the very next day so new flowers showed up.

I had a lot of 'black eyed susans' blossoms after the cold snap even after some covering with frost cloth. The new blossoms took several days to show up.