If you saw the other post the parents were level 2000ish and a 200-300. As long as he hatched the egg after the update/patch it wouldnt have despawned and if he had enough of these eggs duped or just bred and sitting in a fridge they would of hatched , got lucky with one popping around levell 300-400 so it wouldnt despawn, yet ot kept the 1000 melee, just lower level and since its below 450 it wont despawn after updates