I know you can request your own rider record and it will go further back than 2008, but I don't think you can do the same thing for the horse. If your friend is still in contact with his old rider she could request her record (with you friend's horse in it.) Otherwise, maybe a google search?
Just email them and explain your situation and the years you're trying to receive. You should be able to get the report emailed to you. I don't think there's a way that I know of at least that you can search it on their website but they should have the results in their database.
Just email them and say you want your horse's entire show record and they'll email it to you. I did it a few weeks ago, it's super easy. The first time they emailed it to me there was something wrong with the attachment and I couldn't open it, they sent it again by email and said if it still wouldn't open then they would print it and drop it in the mail for me.