My Dh has seen the opposite in two butterfly releases so far (hes a dj) with butterflies being dead and squished on the floor.
I'd heard awful stories about this too so we opted for something a bit different - we had live butterfly centrepieces on all our tables at the reception. They looked amazing and I didn't have to worry about them getting hurt or dying, this would have broken my poor little heart!

At the end of the night the company we hired them from came back to collect them and they were taken back to use as breeding stock, all safe and sound.