I actually had a 5 star get scouted once, and then of all dumb things, I lost him because I started the game without running it as an administrator, so it wouldn't save my freaking game
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I did notice that a cpu team had a complete young stud that I didn't recognize, and after looking at how they got him it was as a scouting discovery. He's 23 now, and had a big season as a 22 year old with 6 WAR. So they are out there, but rightly I think, are few and far between.