Frozen Horse

I am playing pure survival on Xbox and I am at a ruined portal with a horse. I took all the obsidian and by that time it was night. When I went to go mount on my horse it wouldn't let me and I also couldn't hit it. I removed the blocks below it and it is now floating. it is almost like it has barrier blocks around it or it is frozen. I logged off and back on again and now it despawned.