According to this
http://espn.go.com/dallas/story/_/id/8489668/dale-earnhardt-jr-concussion-2-races
concussion happened a couple of weeks ago.
Not sure where you are getting that from that story.
According to Hendrick Motorsports, Jr. definately suffered the concussion on Sunday at Dega.
Now he did take a really hard lick during testing at Kansas in August, and he did suffer a concussion in 2002 in a wreck at California.