Vanishing horse

I was riding a horse (with diamond armor and a saddle) when my dirt blocks became see-through, so I got off the horse and tried to mine the blocks to fix it but it didn't work so i hit save and quit then closed my application. I assumed it was a bug and when I opened minecraft again it would be fixed. I retried again about 5 minutes later and when I joined back my horse was no where to be found. I was on an island so the only place it could have gone was the water so I searched for the horse in the water, and it was still nowhere to be found. If it had died it would had said that but it didn't and now I'm missing one of my fastest horses and a set of diamond horse armor.