on zdnet they have an article on this subject, "VANCOUVER, BC — A pair of European researchers used the spotlight of the CanSecWest Pwn2Own hacking contest here to break into a fully patched iPhone and hijack the entire SMS database, including text messages that had already been deleted."
not sure if it was a 3GS but it sounds like it was 3.1.3 considering they noted "fully patched" in the article........but thats anyones guess. they got to keep the phone tho which is pretty legit