Actually this is first alluded to in season 1's "Infection" when Garibaldi talks to the reporter about how he and Sinclair's shuttle went down and they had to walk back to civilization. IIRC, this is when they first met. I liked how Sinclair wasn't name dropped in the season 3 episode for the sake of name dropping.Garibaldi's story in Messages from Earth was a nice nod to the events of the comic. I wasn't particularly irked that Sinclair wasn't namechecked there.