Disappearance of tamed and created mobs

In my world of survival, I have created 5 golems and 2 of them is missing. One of them has a name tagged and disappeared out of thin air when I was decorating my house ( the golem is place in my house ), one of the golem disappeared when I placed it in my room. Not just golem, animals I already tamed and fed had disappeared on my barn which has fences over them. Also, part of my house was missing when I came back from nether world.