Fading creatures

Hello.

I want to report what I believe is a bug because I can't find an explanation for what's going on. I took a villager by the boat and brought him to live close to me. I made a house and two iron Golems to protect him. Everything was normal until he disappeared with the Golems. I searched the map all over and nothing. The same day when I was taking another villager (because the other one was gone) my wolf disappeared. I wonder if he died, but there was no information in the game chat as it usually appears. And I never left the game, so he disappeared while I was playing. I looked in the same places that I had gone that day, and I didn't find him. Very strange! Days later when I had already made another house and already had other villagers, just the two that I had labeled disappeared on the same day. All of a sudden. I wonder if they died, but it doesn't make sense, because they disappear together on the same day. I counted a total of 6 essential creatures in my game (I needed them) missing.

I was wondering if there is any explanation for this or if it is a bug.