So I've been in Solstheim for a good long while, finished the main quest for Dragonborn, still running around doing a few minor side quests and so forth, when Neloth sends me back to Skyrim on another quest. When I get there, my long time, trusty horse (if not a bit rambunctious when it comes to running into battle---hey Bethesda, horses don't behave that way! Usually in the face of danger, a horse will become a big pile of panic and run away!) Shadowmere, is gone. I left him at the Windhelm stables when I initially set off for Solstheim, and now he's nowhere to be found. I even checked at every house that I've built, in hopes that maybe he's made his way home, but no joy there. Shadowmere is just gone! Help!

One thread is enough.