Board Thread:Skyrim/@comment-108.238.225.145-20150702185707/@comment-6881629-20150702195501

I should add Shadowmere should respawn if you stay well away from the area for that amount of time.

I'm not sure how horses actually go back to their stables but if they literally walk back like a npc would walk home i wouldn't be surprised if the normal horses didn't make it back most of the time. If the horse isn't back at the stable it came from or at place you left it when you got Shadowmere (it shouldn't be though) i'd count that horse as lost unfortunately.