Villagers Dissapear When I Fly Too High In Creative (Flat)

I spawned very many villagers on ground level in a flat world, creative mode, difficulty off, with all of the fancy graphics and render distance and everything on highest. This villigers I spawned were in an in closed building. I then began to build another floating building way high up near the building limit. When I came back down- all of the villagers simply dissappeared! I tried again, spawned at least one hundred villagers in this big square building, enclosed, flew all the way upp, and when I came back down they were gone. This isn't the first weird thing that's happened to mine craft on my phone. This particular seed was (124225).