horse disappearing when attached to lead/fence

I attached my horse to a fence with a lead for a while it had a saddle and it was fine. I rode the horse, gave it armor, and attached to the same fence with a lead, and even fed it. However, when I left and came back, it disappeared. I searched and searched, even copied the world in creative to find it and it was nowhere. I tried to exit out and enter the world again, but it was gone. Foxes I had on leads and fed also disappeared. I was very upset because it had a saddle, armor, and it was an amazing horse, which is hard to find in survival.