I've heard he respawns about a month after he dies in the same location he died at. He just got killed in the wilderness and was wondering where he would likely respawn at, since it wasn't at a specific location but just outside of it.

He respawns after (3?) days at the pool where he first appeared.

How did he die?!? I have been using my shadowmere to level weapon skills/spells on and I can't even get him to 90% before he is back at full...

I was at the Throat of the World, using the blizzard to level my Restoration and Shadowmere decided to run into the storm and stand there. Didn't notice him behind me until he began tumbling towards me (was listening to music; Silent Hill 2 soundtrack makes being up there at night insanely eerie).

He died for me too... I was riding him, while trying to "slowly" go down a mountain side. I slipped. We cratered. Shadowmere died. I shed a tear.

As mentioned before, just go back the DB and he'll be waiting for you.

UESP says he respawns at the location of death.

On my first file she's gone, didn't die, just ran into the wilderness after a monster or something. Never came back, never found anywhere. I checked the sanctuary pool several times, no luck. Just restarted a new game.

I didn't know he respawned