animal disappearance on glass

I have this survival world and on the roof of my house is mostly glass, for the first time I placed 2 llamas 1 sheep and a pig, after i closed the game and came back they are gone, I thought the despawned or something. on the second time I placed a horse on a leash with saddle and putted a name on it, It despawned after a close the game and came back as well.