Oh, so I guess you know that I'm the half-blood prince, huh?

I was in a hotel and met Alan Rickman. This was a few years back, when the 6th book was out, and as he was signing an autograph for me, he asked if I finished the book. Starstruck, I said yes, even though I wasn't. He then says "Oh, so I guess you know that I'm the half-blood prince, huh?" My jaw dropped. I had Snape Personally reveal his true identity to me.