I don't know the artist or the song title BUT I do know where you can find out. The website (http://www.fox.com/oc/home.htm) lists all of the songs they played (except, perhaps, for the music showcase, but you can still watch it on the site) for each episode. Just go to Features>Weekly Soundtrack and download all of the songs listed and you should find it.
Also, do you have any idea when they are going to re-show that episode? I only got to see about 20 minutes of it because I had to be rushed to the hospital (it's the only episode I've ever missed). Now with the new schedule I fear they might not show a repeat of last week's episode :(