Disappearing horse

The other day when I was riding my horse so I could fill out a map I had to leave so my friend could join when I came back I saw myself on my diamond armored horse and my map for half a second then it disappeared but my map dint. I looked all around for my horse and I couldn't find it. To this day I still can't find the horse.
I was expecting to when I went back in to my world to be on my horse holding my map.

I'm including a picture of what my horse looked like: