Hosting a survival world with a friend on mobile, I crashed just after killing a drowned. My friend was about to sit on his horse. After loading the world back up, everything was reverted to about 20 seconds prior, but my mule with a full chest and his horse (both with saddles) had disappeared. I can't hear it in the general area that it was before, so I don't think it's invisible. I have crashed with horses and mules around, but they have never disappeared.