Me and my friend were playing on our Minecraft world, and we found horses, so we tamed them, and gave the a nice pen, however, after a while, the horses despawned, and it wasn't good because the horse armor we gave the horses also despawned as well, we worked on getting more horses to replace the despawned horses, which we got easily. Sadly, nearly all the horses we got and tamed, kept on despawning. We also knew that they weren't killed because they didn't drop anything, and didn't make any sound of being damaged so they randomly despawned without a trace.