You should have at least gotten an e-mail saying if you have been picked you will receive another e-mail in the next couple of days. So if you didn't get the first one then you might have check the wrong e-mail?

I also think the play a bunch of Halo 2 on Live is actually...Play 3 hours of Halo 2 online on a certain day(for some reason I think Feb 15th) and then go sign up online or something. I might have read that one completely wrong but that is what I remember.