I have been having this issue as well. It seems to happen most often when I am forcibly dismounted from the horse when falling into deep water but this may be irrelevant as I have also experienced it when dismounting willingly. The horse reappears upon relog.
I have been having this issue as well. It seems to happen most often when I am forcibly dismounted from the horse when falling into deep water but this may be irrelevant as I have also experienced it when dismounting willingly. The horse reappears upon relog.