I found DPR's altoid account, but I don't see the silk road advert post dated January 29th, 2011. The earliest post is from February 25th, 2011, and is about running bitcoind on Debian...
https://bitcointalk.org/index.php?action=profile;u=3905;sa=showPosts;start=40I suspect DPR deleted the post (wouldn't you?) and the FBI found it by requesting logs from bitcointalk admins.
Theymos, can you confirm?