After 100 hours of being parted from my shadowmere because she wandered off and never returned. I randomly jumped off the waterfall above that fisherman's cottage south west of morthal and at the bottom was shadow mere. This could possibly one of the most random events yet.

Ok

Kool, glad you decided to share.

Sounds like she spooked when that dragon attacked and ran off like a smart horse.

or you left him there last time

Glad to know she returns. I lost her when fighiting a dragon. Killed it, teletported off and no more Shadowmere. Either she's dead or disapeared from the game. I hope she returns.

I have an over-excessive saving habit just to make sure, if she ever disappears, BOOM, re-load to a save I done 90 seconds ago.

I never got my Shadowmere. I walked out of the DB Sanctuary and the water bubbled and smoke arose and I heard a neigh. But there was no horse to be found =\

Go back to the old dark brotherhood place and it should appear there - happened to me a couple times