My platy was showing all the signs of being pregnant, so we had it checked and she was. But when it came to the day, she had eggs in a sack and it took two days for them to come out completely. However, we were told platies had live birth.
Yes, platys give live birth, but this only means the eggs hatch inside the fish, before the babies and the broken membranes are born.
What I think might have happened is the embryos inside the eggs died, so the fish released the dead eggs. This does happen from time to time. It can be because of stress or as a result of bad water quality.