I could pretty much guarantee that your fry is/was a platy. They are almost always gravid when you purchse them if they were being kept in a mixed gender tank. I don't know about the eggs though. Fry don't often last in a community tank though. Sometimes if you prvide enough cover you will have some survivors. Livebearers first drops are often really small, so it is more likely for all the for to get eaten because every individual fry stands out like it has an "eat me" sign taped to it. Bur, fry can survive if they are good hiders.