So at that time, I raised animals, such as cows, there were two cows and I fed them with wheat. Then, They Have Baby Cows, So There Are Three Cows. And I quit the Minecraft game, just for a second. After that, I got back into his Minecraft game and entered my world. And I went to the stable to check my cow, suddenly all the cows disappeared, and disappeared mysteriously. This is a bug from the Minecraft game version, 1.16.221 Official