QUOTE(blackhawk226 @ May 25 2008, 12:14 AM)

You are gonna have to ask him where he got off the horse to fast travel and where he fast travelled to. Naturally, the horse should be around there if it is dead, also the unicorn will never belong to you even if you get on it. Check on the most direct route to the grove from the spot where he left the unicorn. That seems to be the most valid choice. Good luck!
This is the best advice I've read.
If you are able to save using the PS3 version try a previous save, if there is no previous saves but you are able to save I suggest save the game before you start your search that way you can fan out your search & use as little time as possible.
For instance the shortest distance from point A to point B is a straight line right.
So you make your first search be as Blackhawk suggest straight to the groove as possible.
If you don't find it reload the save & make your new search path a little to the right of the original one.
If you still don't find it reload again but this time make the search path to the left of the original.
Using this method you could theoretically continue to make a broader & broader search & still not loose any in-game time.
Best of luck to you both.