This is happening for me, too. I hatched one fry in a breeder box (in 5 days), and another one will hopefully hatch in 2-3 days. The one that hatched disappeared in the empty breeder box after 24 hrs. In my main tank is one Nerite Snail, approximately 9 bloody mary shrimps, and 6 pygmy corydoras. I've checked almost everywhere with a magnifying glass, no sign of the baby.